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2_hydraulic_system_operation_w_flow_charts

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80 views106 pages

843

2_hydraulic_system_operation_w_flow_charts

Uploaded by

Alain Defoe
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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(e961 soquenon perma) oizosse¥ wu —- YOON (666ZL "UL LOOLL N/S) EPS tepow 103 AMVHD MOTS SILVLSOUGAH / STINVEGAH 2 HYDRAULIC / HYDROSTATIC SYSTEM OPERATION To Be Used With HYDRAULIC / HYDROSTATIC FLOW CHART For Model 843 (S/N 11001 Thru 12999) Chart # 6566716 (Printed November 1988) @ FLUID RESERVOIR, 6.0 Gals. (22,7 L) - 3:5-4.0 Gal. 413,2-15,1 Lb 15 cu. in. (246 cm’) HYDROSTATIC PUMP @ HIGH PRESSURE RELIEF REPLENISHING VALVES, ... 3500 PSI (24132 kPa) @ HypRAUUC PUMP, 15.4 GPM (58,3 Lihin,) at 2720 RPM © TEMPERATURE SWITCH, ... 210°F. (99°C) @ Port BLock © RELIEF VALVE, . ‘TILT CYLINDER (Cushioned) @ urt cruNnDeERS © onirice, 0.098" {2,51 mm) Dia. SN 11935 2 Below ORIFICE, .... 0.138" (3,51 mm) Dia. Starting With SN 11936 © HYORAUYC CONTROL VALVE, Self-Level 2325-2500 PSI (Measured at Quick © RESTRICTOR (In Float and Lower Position Only) @ PORT RELIEF (Lift Section) 3500 PSI (24132 kPa) @ auxwiary auick CouPLERS @ PUTER... 2-2. 10 Micron es0s718 01-80 (Sheet 2 Of 21 CHART LEGEND —=======—=—=-——___— @© FILTER BY-PASS, .. 30 PSI (207 kPa @ on cooLer @ PRESSURE SWITCH, .... 2.5-3.5 PSI 117,3-24,1 kPa} @ BY-PASS VALVE, ....- 180-200 PSI (1241-1379 kPa) @ ACCUMULATOR, Nitrogen Precharge 120 PSI (827 kPa} (Starting at ‘S/N 11936) Printed i US.A, OlL FLOW EXPLANATION ==-— ‘The fluid flows from the reservoir @ to the inlet of the port block @ . Reservoir fluid is joined by the hydrostatic motor @ case drain and the retum fluid from the oil cooler @ This combined flow. supplies fluid to the hydraulic pump @ ‘The hydraulic pump © (a “gear” typel forces the fluid to the hydraulic control valve When all three spools are in neutral position, the fluid goes through the control valve @ and either to the reservoir @ or ta the port block @ . The hydraulic control valve @ isa three section, parallel open center, closed port valve with a main relief vatve @ built into the inlet section of the control valve @ When one of the spools is dctivated, the fluid flow is directed to either the base end or the rod end of the cylindetts)@ @. Return fivid from the other end of the cylinderts) @ @ goes back to the hydraulic control valve @ and goes to the 40 micron inthe port block @ . The “tee” fitting at the outlet of the control valve @ allows fluid to return to either the by-pass valve @ and to the fluid reservoir @ through a diffuser ‘01 to the 40 micron fitter @ in the port block @ during normal operation. *The “tee fitting also connects to an accumulator @ which will provide a temporary charge pressure flow ‘when the lift and tilt cylinders are being extended. Two sections on the control valve @ can be used at the same time if the main relief valve @ is not open. “The accumulator @ is standard beginning with serial number 11936, ‘The by-pass vatve @ will open during cold weather or if there is excessive fluid pressure. The normal fluid flow through the 40 micron filter @ , goes by the temperature switch @ ‘and against the neutral charge by-pass valve @ . The normal flow is through the ‘“tee’’ fitting between the temperature switch @ and the charge by-pass valve @ to the front ‘and the rear hydrostatic pumps @ . The fluid flow is caltad “charge pressure” and supplies the hydrostatic pumps @ and the hydrostatic motors @ with charge fluid. The charge fluid is used by the pump and motor, but as the charge pressure increases, the charge by-pass vatve @ will open to prevent excessive pressure built up. ‘The neutral charge fluid flows into each hydrostatic pump © and hydrostatic motor @ to cool, lubricate and replenish the fluid supply which is fost through case drain. Hydrostatic pumps © case drain flows into the inlet side of the hydraulic pump © through intemal porting. ‘There are two hydrostatic pumps @ and two hydrostatic motors @ . One pump and one Motor work together as a pair to drive on one side of the loader. The other pump and motor work as 2 pair to drive the opposite side of the loader. ‘When the hydrostatic pumps @ , swashplate are angled in either direction, the hydrostatic pumps @ force fluid, under high pressure, to the hydrostatic motors @ . The hydrostatic motors @ turn and push the low pressure fluid back to the hydrostatic pumps @ to’be used again. The hydrostatic motors @ also contain a shuttle valve to allow some of the fluid from the “drive loop’ to go to the oil cooler @ for cooling. The hydrostatic pumps © center section contains four high pressure relief/replenishing valves @ . Two for each side, one for forward travel and one for reverse travel. The high pressure ‘replenishing valves @ have a dual function. In neutral the valve cartridges @ are pushed off their Seats to allow fluid flow from the charge loop to the cool, lubricate and replenish the pumps and the motors. When the swashplates are angled, the fluid is at a higher pressure than the charge fluid, this pressure difference causes the high pressure replenishing valves @ to be forced against the seats. The high pressure replenishing valves @ also act as a high pressure relief valve for the hydrostatic pumps @ , in case of excessive pressure being generated by the hydrostatic pumps @ . The high pressure replenishing valves @ will open allowing the “drive pressure" to relieve into the charge loop to be used again. Excess charge pressure fluid which is relieved over the charge by-pass valve @ is routed to the “tee"’ and joins the hydrostatic motor @ case drain fluid and flows to the oil cooler @ . The “tee” fitting has a pressure switch @ that senses a drop in pressure of the fluid which goes to the oil cooler @ . Fluid from the oil cooler @ flows through the filter @ which has a built in by-pass valve @ . The fluid then flows into the inlet of the port block and back to the hydraulic pump @ . 2 (eaci soqusron poms aer29s98 wD YO0GOQ, omg our] ofteya pur 2oenUNDay pM) 3% "POW 204, AMVH9 MO1d DLLVASOUGAH / OTINVEGAH * *" bobcat HYDRAULIC / HYDROSTATIC SYSTEM OPERATION ‘To Be Used With HYDRAULIC / HYDROSTATIC FLOW CHART For Model 843 (S/N 13001 Thru 14999) (With Accumulator and Charge Line Filter) ‘Chart # 6566748 (Printed November 1988) - CHART LEGEND @ FLUID RESERVOIR, @ on. cooLen Cap... + 6.0 Gals. (22,7 L) @ ORIFICE RESTRICTOR, ..... 0.275" Working Cap. 3.5-4.0 Gal. {6.99 mom) Dia. “(13,2:15.1L) @ PRESSURE SWITCH, .... 2.5-3.5 PSI @ HYDROSTATIC MOTOR, .. 15 cu. tg (17,3-24,1 kPa) {246 cm"} @ BY-PASS VALVE, ..... 180-200 PS! @ Hvorostatic pump @ HIGH PRESSURE RELIEF REPLENISHING VALVES, ... 3500 PSI (24132 kPa) @ tyoRauuc PUMP, wits: 15.4 GPM (58,3 Lenin.) at 2720 RPM @ TEMPERATURE SWITCH, 225-232°F, (108-130°C) @ PorT BLOCK © RELIEF VALVE, . .. 43-57 PSI “(296-393 kPa) Qrusen ............. eee aS @ birreneNTIAL PRESSURE SWITCH, 19 PSI (131 kPa) @ TILT CYLINDER (Cushioned) @ Uirt CYUNDERS @ FILTER BY-PASS, .. 25 PSI (172 kPa} @ Main REUEF, ...... 2125-2225 PSI (14651-16341 kPa) © onIFIce,.. 2099" (2.51 mm) Dia, @ PORT RELIEF (Lift Section) 3500 PSI (24132 kPa) @ HyoRAuUC CONTROL VALVE, Saif Level ‘AUXILIARY QUICK COUPLERS @ ACCUMULATOR 9809748 (11-80) (Sheet 2 OF 2) (1241-1379 kPa) Primed ia U.S.A OIL FLOW EXPLANATION The fluid flows from the reservoir @ to the intet of the port block @ . Reservoir fluid is joined by the hydrostatic motor @ case drain and the return fluid from the oll cooler © . This combined flow supplies fluid to the hydraulic pump @ The hydraulic pump @ (a “gear" type) forces the fluid to the hydraulic control valve @ . ‘When all three spools are in neutral position, the fluid goes through the control valve @ and either to the reservoir @ or to the part block @ . The hydraulic control valve @ is a three section, parallel open center, closed port vatve with a main relief valve @ built into the inlet section. When one of the spools is activated, the fluid flow is directed to either the base end or the rod end of the cylinders) @@. Return fluid from the other end of the cylinderis} @ @ goes back to the hydraulic control valve © and through the 3 micron Finer @ and back to the port block @ . The “tee” fitting at the outlet of the contro! valve @ silows fluid to retum to either the by-pass valve @ and to the fluid reservoir @ through a diffuser or through the #3 filter @ and to the port block @ during ‘normal operation. *The “tee” fitting also connects to an accumulator @ which will provide ‘a temporary charge pressure flow when the lift and tilt cylinders are both being extended. Two sections on the contro! valve @ can be used at the same time if the main relief vaive @ is not open. The by-pass valve @ will open during cold weather or if there is excessive fluid pressure. ‘The flow of fluid is through the #3 filter @ , into the port block @ , past the temperature switch @ and against the neutral charge by-pass valve @ . The normal flow is through the “tee” fitting between the temperature switch @ and the charge by-pass valve @ to the front and the rear hydrostatic pumps @ . This fluid flow is called “‘charge pressure” and supplies the hydrostatic pumps @ and the hydrostatic motors @ with charge fluid. The charge tlvid is used by the pump and motor, but as the cherge pressure increases, the charge by-pass valve @ will open to prevent excessive pressure build up. ‘The neutral charge fluid flows into each hydrostatic pump © and hydrostatic motor @ to ‘cool, lubricate and replenish the fluid supply which is lost through case Case drain from the hydrostatic pumps @ flows into the inlet side of the hydraulic pump @ through internal porting. ‘There are two hydrostatic pumps @ and two hydrostatic motors @ . One pump and one ‘motor work together as a pair to drive one side of the loader. The other pump and motor work as 2 pair to drive the opposite side of the loader. When the swashplates, of the hydrostatic pumps @ , are angled in either direction, the hydrostatic pumps @ force fluid, under high pressure, to the hydrostatic motors @ . The hydrostatic motors @ turn and push the tow pressure fluid back to the hydrostatic pumps @ to be used again. The hydrostatic motors @. also contain a shuttie valve to allow ‘some of the fluid from the drive loop to go to the oll cooler @ for cooling. The hydrostatic pumps @ center section contains four high pressure relief/replenishing valves @ . There: are two for each side; one for forward travel and one for reverse travel. The high pressure replenishing valves @ have # dual function. in noutral the valve cartridges @ are pushed Off their seats to allow fluid flow from the charge loop to the cool, lubricate and replenish ‘the pumps and the motors. When the swashplates are angled, the fluid is at a higher pressure than the charge fluid, this pressure difference causes the high pressure replenishing valves @ to be forced against the seats. The high pressure replenishing valves @ also act as a high pressure relief vaive for the hydrostatic pumps @ , in case of excessive pressure being generated by the hydrostatic pumps @ . The high pressure replenishing vatves @ wilt open allowing the “drive pressure" to relieve into the charge loop to be used again. Excess charge pressure fluid which is relieved over the charge by-pass valve @ is routed to the “tee” block and joins the hydrostatic motor @ case drain fluid and flows to the oll cooler @ . The “tee” fitting has a pressure switch @ that senses a drop in pressure of the fluid which goes to the oil cooler @ . Fluid from the oil cooler @ flows into the inlet of the port block @ and back to the hydraulic pump @ . BEE MRT OTHE Ee, PRP "ye ‘erent 23 AMVHD MO1S DILVISONGAH / ONINVUGAH oe OY) o x ‘bobcat HYDRAULIC / HYDROSTATIC SYSTEM OPERATION To Be Used With Pe HYDRAULIC / HYDROSTATIC FLOW CHART For Model 843 (S/N 15001 Thru 25999) Chart # 6570242 (Printed Apeit 1986) @ RESERVOIR, Cap:..... 3.5-4.0 Gals. 193,2-15,1 L) @ TEMPERATURE SWITCH,. 225-232°F (108-111°C) @ COLD OIL BY-PASS VALVE,.. 297 PSI (2048 kPa) @ Pont sLock @ CHARGE BY-PASS VALVE, @ ORIFICE... Motor Case Drain 0.217" (5,51 mm) Dia. @ tyDROsTaTiC MoTOR @ PRESSURE SWITCH (Dual Function), Hourmeter Starts @ 19-23 PSI (132-158 kPa) Waring Light Tums off @ 17-21 PSI (118.144 kPa) © HYDRAULIC PUMP, Gear Type ‘8. Charge Pump, 11.5 GPM (43,5 Limia.) @ 2700 RPM @ 1050 PSI (7239 kPa) b. Hydraulic Pump, 16.1 GPM (60,9 Limin.) @ 2700 APM @ 1050 PSI (7239 kPa} © HYDRAULIC AUXILIARY LINES @ urT CYLINDERS @ TILT CYLINDERS @ LOAD CHECK VALVES (Four) @ ANTL-CAVITATION CHECK VALVE © onIFicE @ MAIN RELIEF VALVE,._ 2250-2400 PSI (15514-16548 kPa) @ PORT RELIEF VALVE...... ‘3600 PSI (24132 kPa) @ HYDRAULIC CONTROL VALVE © BUCKET POSITION VALVE @ FLow-coNTROL SPOOL @ CHECK VALVE (0570242 (1.86) Reed 1-36) (Sheet 2 0f 2) CHART LEGEND —=——$————— @ PRESSURE RELIEF VALVE @ UN-LOADING SPOOL @ FIDER, Hydraulic. @ BY-PASS VALVE. @ oi CooLeR @ FITTER, Hydrostatic... . . #3 Elemen @ DIAGNOSTIC COUPLER © PRESSURE SWITCH, Differential ‘S/N 15001-20991 — 19 PSI (131 KPa) ‘Starting W/ SIN 20992 — 40PSI (276 kPa @ BY-PASS VALVE, ‘SIN 15001-20991 — 25 PSI (172 kPa! Starting W/ S/N 20992 — SOPSI (345 kPa ++ #10 Microt 72 PSI (496 kPa @ DeFUSER @ SCREEN... = 100 Mest @ GREATHER CAP... 5 Micror @ tyoRosTATIC PUMPS @ HIGH PRESSURE RELIEF VALVES ‘3500 PSI (24133 kPa Printed USA OIL FLOW EXPLANATION — ‘The fluid reservoir @ is filled by removing the breather cap @ and filing fluid through the 100 mesh screen . Hydraulic fluid flows from the reservoir @ and enters the inlet port of the tandem {2 sections) gear pump @. ‘The larger section of the tandem pump supplies pressure to the infet of the hydraulic contro! valve © . The pump pressure is controlled by the main relief valve @ . The contro! valve @ is 8 four-section, open center, closed port, series type valve. When all four spools are in neutral position, the fluid goes through the control valve @ and either to the hydraulic filter @ or to the bucket position valve © . ‘The lift section and titt section of the control valve @ work together to position the bucket as the fift arms of the loader are being raised. When the lift arms are being raised, the hydraulic pump @" flow is directed to the base end of the fift cylinders @ . The fluid from the rod end of the lift cylinders @ retums into the bucket position valve @ and is directed to the center of the flow-cantral spoo! @ . The flow-control spoo! @ has an orifice ateach end. Fifty nine percent (59%) of the fluid flow is directed to the base end of the tilt cylinder @ . Forty one percent (41%) of the fluid is directed through the opposite end of the flow-control spool @ and to the return port of the control valve @ lift section. ‘The fifty nine percent {58%} of the fluid flow from the flow-control spool @ is against the unloading ‘spool @ and a check valve @ . An increase in fluid pressure causes the check valve @ to open which allows the flow of the fluid to the base end of the tilt cylinder ® . The fluid from the rod end of the tilt cylinder @ is contained by the untoading spool @ until the tit cylinder base end @ pressure is high enough to open the un-loading spoot @ and allow the rod end fluid to retum into the contro! vaive @ . The pressure relict valve @ is to relief fluid from the base end of the tilt cylinder @ if the bucket is fully rolled out and lift cylinders @ are stif extending. ‘The fluid flows from the charge pump @" either to the oi cooler @ or to the cooler by- pass valve @ will open when the fluid temperature is low or if there is excessive fluid pressure. The fluid flows through the oll cooler @ then through the hydrostatic filter @ and into the four-way cross fitting. The. fluid tlows past the pressure switch @ to the charge by-pass valve @ . The pressure switch @ has a dual function, it starts the hourmeter and tums the warning light off. ‘Normal flow of fluid is through the four-way cross fitting to the front and rear hydrostatic pumps @. This fluid flow is called “charge pressure” and supplies the hydrostatic pumps @ and the hydrostatic motors @ with charge fluid. The charge fluid is used by the pump and motor, but as the charge pressure increases, the charge by-pass valve @ will open to prevent excessive pressure build up. ‘The charge fluid flows into each pump @ and motor @ to cool, lubricate-and replenish the fluid supply which is lost through case drain. Case drain from the pumps @ flows into the intet side of the hydraulic pump @ through internal porting. There are two hydrostatic pumps @ and two hydrostatic motors @ . One pump and one motor work together as a pair to drive one side of the loader. The other pump end motor work as a pair to drive the opposite side of the loader. ‘The the swash plates of the hydrostatic pumps @ are angled in either direction, the pumps @ force fluid, under pressure, to the motors @ . The motors @ tum and push the low pressure fluid back to the pumps @ to be used again. The motors @ contain a shuttle ‘valve which allows some fluid from the “drive loop” to go to the port block @ and back to the reservoir @ . The hydrostatic pumps @ contain four high pressure eliel/replenishing valves @ . There are two valves @ for drive on each side of the loader: one for forward ‘travel and one for raverse travel. The high pressure reliet/replenishing valve @ have a dual function. in neutral the valve cartridges © are pushed off their seats to allow fluid flow {rom the charge loop to cool, lubricate and replenish the pumps and motors. In forward ‘or reverse (when the swashplates are angled), the fluid has a higher pressure than charge fluid, This pressure difference forces one of the high pressure replenishing valves (one per pump) @ against the seat. Tho high pressure replenishing valves @ also act as a high pressure refiel valve for the hydrostatic pumps @. The high pressure replenishing valves @ will open allowing the “drive pressure” to relieve into the charge loop to be used agein if excessive pressure is generated by the pumps @ . ‘Excess charge pressure fluid which is relleved over the charge by-pass valve @ goes through the port block @ and joins the hydrostatic motors @ case drain fluid and flows to the reservoir @ through the defusser @ . Fluid from the cold oil by-pass valve @ flows into the port block @ and back to the reservoir @ . Both the hydraulic fiter @ and the hydrostatic filter @® have a by-pass valves. The hydraulic. filter @ has » 72 PS! (496 kPa) by-pass velve @ . The hydrostatic fitter @ has a 25 PS! (172 kPa} (S/N 15001-20991) or 50 PSI {345 kPa) (Starting at SIN 20992) by-pass vaive @ and also contains a pressure differential switch @ which indicatés the condition of the filter. ‘The diagnostic coupler ® provides a quick access for checking the charge pressure. seman = 0909, sa zesoragg ve meng a Ba eeee aa oboe NS toe 4 eee ANVHD MOT OUYLSOUGAH / OTIAWEGAH Foca HYDRAULIC / HYDROSTATIC SYSTEM OPERATION To Be Used With HYDRAULIC / HYDROSTATIC FLOW CHART For Mode! 843 (S/N 26001 Thru 29925) (Chart #6570552 (Printed May 1989) © RESERVOIR, Cap:..... 3.5-4.0 Gals, (13,2-45,1 L) @ TEMPERATURE SWITCH, . 225-232°F (tosti1°c) @ COLD FLUID BY-PASS VALVE, 297 PSI (2048 kPa) @ CHARGE BY-PASS VALVE,... 110 PSI (758 kPa) @ ORIFICE... Motor Case Orein 0.217" {6,51 men} Dia. @ HypRostanc moTOR © PRESSURE SWITCH (Dua! Function), Hourmeter Starts @ 19-23 PSI (131-159 kPa) Warning Light Tums off @ 17-21 PS1 (117-445 kPa} @ HYDRAULIC PUMP, Gear Type. 8, Charge Pump, 11.6 GPM (43,5 Liming) @ 2700 RPM @ 1050 PSI (7240 kPa) Hydraulic Pump, 16.4 GPM (60,9 Limin) @ 2700 RPM @ 1050 PSI (7240 KPa) @ PORT RELIEF VALVE... ... 3500 PSI (24133 kPa) © HYDRAULIC CONTROL VALVE ‘CHART LEGEND @ PRESSURE RELIEF VALVE @ UN-LOADING SPOOL @ FILER, Hydraulic. @ BYPASS VALVE @ on cooten @ FALTER, Hydrostatic... .. @ DIAGNOSTIC COUPLER PRESSURE SWITCH, Differential ‘SIN 15001-20991 — 19 PSI (131 kPa) Starting W/ SIN 20982 — 40PS1(276KPa) @ BY-PASS VALVE, ‘SIN 16001-20991 — 25 PSI (172 kPa) Starting W/ SAV 20882 — 60 PSI (345 Pa) +++ #10 Micron 72 PSI (496 kPa) #3 Element @ pirruseR ‘SCREEN... 00 Mesh @ BREATHER CAP . 5 Micron @ HYDROSTATIC PUMPS @ HIGH PRESSURE RELIEF VALVES 3500 PSI (24133 kPa) @ STEERING SERVO VALVE (2) 6570882 15.09 (Shoot 2 Of 2) Printed USA. = OIL FLOW EXPLANATION ——=—— Hydraulic fluid flows from the reservoir @ and enters the inlet part of the tandem (2 sections) gear pump © . The larger saction @" of the tandem pump supplies pressure to the inlet of the hydraulic control valve @ . The pump pressure is controlled by the mai relief valve @ . The control valve @ is 2 four-section, open canter, closed port, series type valve. When all four spools are in neutral position, the fluid goes through the control valve @ and to the hydraulic fitter @ . The lift section and tilt section of the control valve @ work together to position the bucket ‘as the lift arms of the loader are being raised. When the lift arms are being raised, the hydraulic pump @ flow is directed to the base end of the lift cylinders @ . The fluid from the rod end of the lift cylinders @ retums into the bucket position valve @ and is directed to the center of the flow-control spoot @ . The flow-control spoo! @ has an orifice at each end. Forty one percent (41%) of the fluid flow is dirocted through the opposite end of the flow-control spoot @ and to the retum port of the conteal valve @ lift section. Fifty nine percent (59%! of the fluid flow from the flow-control spoo! @ is against the undoading spoo! @ and a check valve @ . An increase in fluid pressure causes the check valve @ to open which allows the flow of the fluid to the base end of the tilt cylinder @ The fluid from the rod end of the tlt cylinder @ is contained by the un-loading spoo! @ unti! the tilt cylinder @ base end pressure is high enough to open the un-loading spoo! @ and allow the rod end fluid to return to the control valve @ . The pressure relief valve @ is to relieve fluid trom the base ond of the tilt cylinder @ if the bucket is fully rolled out and the lift cylinders @ are siill being extended. The fluid from the charge pump section @" flows to either the oil cooler or to the cooler by-pass valve @ . The cooler by-pass valve @ will open when the fluid temperature is tow (cold) or if there is excessive fluid pressure. The fluid flows through the oil cooler @ , then through the hydrostatic filter &@ and into the four-way cross fitting. The fluid flows past the pressure switch @ to the charge by-pass valve @ . The pressure switch @ has dual function, it starts the hourmeter and turns the waming fight off. Normal flow of fluid is through the four-way cross fitting to the front and rear hydrostatic pumps @ , and also supplies fluid to actuate the steering servo controls @ . This fluid flow is called charge pressure fluid. The charge fluid flows into esch pump @ and motor @ to coat, lubricate and replenish the fluid supply which is lost through case drain. Case drain from the pumps @ flows into the inlet side of the hydrautic pump @ through intemal porting. The return fluid from the steering servos @ flows to the port block @ . There are two hydrostatic pumps @ and two hydrostatic motors @ . One pump and one ‘motor work together as a pair to drive one side of the loader. The other pump and motor work as a pair to drive the opposite side of the loader. ‘The swash plates of the hydrostatic pumps @ are angled by the steering servo xalves.@ in either direction, the pumps @ force fluid, under pressure, to the motors @. The motors @ turn and push the low pressure fluid back to the puinps @ to be used again. The motors @ contain a shuttle valve which allows some fluid from the drive loop to go to the port block @ and back to the reservoir @ . The hydrostatic pumps @ contein four high pressure relief/replenishing valves € . There aro two valves @ for drive on each side of the loader: one for forward travel and one for reverse travel. The high pressure relief /replenishing valves @ have a dual function. The valve cartridges @ are pushed off their seats to allow fluid flow from the charge loop to cool, lubricate and replenish the ‘pumps and motors. In forward or reverse (when the swash plates are angled), the fluid has 2 higher pressure than charge fluid. This pressure difference forces the high pressure replenishing velves @ onto the seat. The high pressure replenishing valve @ will open allowing the drive pressure to relieve into the charge loop to be used again if excessive pressure is generated by the pumps @ . Excess charge pressure fluid which is relieved over the charge by-pass valve @ goes through the port block @ and joins the hydrostatic motors @ case drain and flows to the reservoir @ through the diffuser @ . Fluid from the cold oil by-pass valve @ flows into the port block @ and back to the reservoir @ under conditions of cold fluid or excess flow. ‘The hydraulic filter @ has a by-pass valves to protect the system if the filter element becomes plugged. The hydrostatic filter @ has a by-pass valve and a pressure differential switch @ which indicates the condition of the filter element. The diagnostic coupler @ provides a quick access for checking the charge pressure in the system. pon 203 AHVHO MO1d DLIVLSOUGAH / STINWHGAH oe oe Bcect HYDRAULIC / HYDROSTATIC SYSTEM OPERATION To Be Used With HYDRAULIC / HYDROSTATIC FLOW CHART For Model 843 (SIN 29926 & Above) ‘Chart #6720178 (Printed May 1989) CHART LEGEND @ RESERVOIR, Cap:..... 3.5-4.0 Gals. @ UN-LOADING SPOOL (13,2461 L) — @ FILTER, Hydraulic....... #10 Micron © TEMPERATURE SWITCH,. 225-232°F @ BY-PASS VALVE... 72 PSI (496 kPa) (08-411°C) @ on cooLer © COLD FLUND BY-PASS VALVE, 297 PSI @ FUTER, Hydrostatic..... #3 Element (2048 kPa) @ piaGNosmic COUPLER PRESSURE SWITCH, Differential © chance evens vave,... roest © “40 PSI (276 kPa) (768 kPa) « 60 PSI (345 kPa) © ORIFICE... Motor Case Drain 0.217” (5,51 mm) Dia. @ HyoRosTanc moTOR @ PRESSURE SWITCH (Dust Function), Hourmeter Starts @ 19-23 PS! (131-159 kPa) Warning Light Turns off @ 17-21 PS! (117-145 kPa) © HYDRAULIC PUMP, Gear Type ©. Charge Pump, 11.5 GPM (43,5 Limin.) @ 2700 RPM @ 1050 PSI (7240 kPa) b Hydraulic Pump, 161 GPM (60,9Limin) @ 2700 RPM @ 1050 PSI (7240 kPa} @ HYORAULIC AUXILIARY LINES ‘LUFT CYLINDERS, © Tur CYLINDER @ LOAD CHECK VALVES (Four) @ ANTI-CAVITATION CHECK VALVE @ MAIN RELIEF VALVE, 2250-2400 PS! (15514-16548 kPa) @ PORT RELIEF VALVE...... 3500 PSI (24133 kPa) © HYDRAULIC CONTROL VALVE BUCKET POSITION VALVE FLOW-CONTROL SPOOL @ FLOW ADJUSTMENT VALVE sr20778 609 (Sheet 2 OF 2) 100 Mesh - 5 Micron @ HYDROSTATIC PUMPS @ HIGH PRESSURE RELIEF VALVES ‘3600 PSI (24133 kPa) ‘@ STEERING SERVO VALVE (2) Plate ta USA. OIL FLOW EXPLANATION Hydraulic fluid flows from the reservoir @ and enters the inlet port of the tandem (2 sections} gear pump @ . The larger section @ of the tondem pump suppltes pressure to the inlet of the hydraulic control valve @ . The pump pressure is controfled by the main relief valve @ . The control valve @ is s four-section, open center, closed port, series type valve. When all four spools are in neutral position, the fluid goes ‘through the control valve @ and to the hydraulic fitter @ . ‘The lift section and tilt section of the control valve @ work together to position the bucket 2s the lift arms, of the loader, are being raised. When the lift arms aré being raised, the hydraulic pump @? fluid flow is directed to the base end of the lift cyfinders @ . The fluid from the rod ond of the lift cylinders @ returns to the bucket position valve @ and is directed to the center of the flow-contro! spool! @. The flow-control spool @ and adjustable metering orifice @ split this flow. Fifty-nine percenit (59%! of the fiuid flow is directed over the metering orifice @ to tevel.the bucket. Forty-one percent (41%) of the fluid is directed through the orifice in the flow-control spool! @ and on ta the return port of the control vatve {lift section) © . Fifty nine percent (59%) of the fluid flow from the flow-control spoo! @ and metering orifice @ is against the untoading spool @ . The un-toading spoa! moves to éllow extension of the tilt cylinder @ as the lift cylinders @ raise the lift arms. ‘The fluid from the charge pump section @* flows to either the oil cooter @ or to the cooler by-pass valve @ . The cooler by-pass valve @ will open when the fluid temperature {slow (cold) or if there is excessive fluid pressure. The fluid flows through the ail cooler @ , then through the hydrostatic filter @ and into the four-way cross fitting. The fluid flows past the pressure switch @ to the charge by-pass valve @ . The pressure switch @ hes ‘a dual function, it starts the hourmeter and tums the warning light off. Normal flow of fluid is through the four-way cross fitting to the front and rear hydrostatic pumps @ , and also supplies fluid to actuate the steering servo controls @ . This fluid flow is called charge pressure fluid. The charge fluid flows into each pump @ and motor @ to cool, lubricate and replenish the fluid supply which is lost through case drain. Case drain from the pumps @ flows into the inlet side of the hydraulic pump @ through internal porting. The retum fluid from the steering servos @ flows to the port block @ . ‘There:are two hydrostatic pumps @ and two hydrostatic. motors @ . One pump and one motor work together as a pair to drive one side of the loader, The other pump and motor work as a pair to drive the opposite side of the loader. The swash plates of the hydrostatic pumps @) are angied by the steering servo valves @ in either direction, the pumps @ force fluid, under pressure, to the motors @ . The motors @ tum and push the tow pressure fluid back to the pumps @ to be used again. The motors @ contain a shuttie valve which allows some fluid from the drive loop to go to-the port block @ and back to the reservoir @ . The hydrostatic pumps @ contain four high pressure reliefireplenishing valves @ . There are two valves @ for drive on each side of the loader: one for forward travel and one for reverse travel. The high pressure relief/replenishing valves @ have a dual function. The valve cartridges @ are pushed off their seats to allow fluid flow from the charge loop to cool, lubricate and replenish the pumps and motors. th forward or reverse (when the swash plates are angled), the fluid has a higher pressure then charge fluid. This pressure difference forces the high pressure replenishing valves @ onto the seat. The high pressure replenishing valve @ will open allowing the drive pressure to relieve into the charge loop to be used again if excessive pressure is generated by the pumps @ . Excess charge pressure fluid which is relieved over the charge by-pass valve @ goes through the port block:@ and joins the hydrostatic motors @ case drain and flows to the reservoir @ through the diffuser @ . Fluid from the cold oil by-pass valve @ flows into the port block @ and back to the reservoir @ under conditions of cold fluid or excess flow. ‘The hydraulic fiiter @ has a by-pass valve @ to protect the system if the fitter element ‘becomes plugged. The hydrostatic fiter € has a by-pass valve @ and a pressure differential switch @ which indicates the condition of the filter element. The diagnostic coupler @ provides a quick access for checking the charge pressure in the system. 2 “und region 5 do pe 00 9 ons ‘t smprponan sap ban os : $ J (eae nw poss sigorsss win —-«-YOGOD, (wnolido) we ‘SONINVHGAH HIMOdISHOH HOIK EPs POW 103 WVUDVIG ONIIA ONY AMVHO MOT OLIVLSOWGAH / OTIAVvEGAH Fever HYDRAULIC / HYDROSTATIC SYSTEM OPERATIONS ‘To Bo Used With HYDRAULIC / HYDROSTATIC FLOW CHART AND WIRING DIAGRAM For Model é 843 HIGH HORSEPOWER HYDRAULICS (OPTIONAL) Chart #6570916 (Printed September 1990) CHART LEGEND @ RESERVOIR, Capacit . 3.6-4.0 Gals. © “ORIFICE, . . . 0.024” (0,61 mm) Dia. (13,2451 ) @ PORT RELIEF VALVE, . -3500 PSI © TEMPERATURE SWITCH,. 225-232°F (24132 KPa) (100-111°C) @ MAIN RELIEF VALVE (Electrical Controlled), @ COLD FLUID BY-PASS VALVE, 297 PSI Normal Operation; 2200 PSI (15159 kPa) 12048 kPal High Horsepower Operation: 3000 PSI @ Port BLOCK (20685 kPa} © CHARGE BYPASS VALVE... 110 PS| @ ORIFICE {758 kPa), @ ELECTRICAL SELECTOR VALVE @ ORIFICE... Motor Case Drain 0.217” @ “RELIEF VALVE, 3000 PS! (20685 kPa) {5,5 mm) Diameter @ UN-LOADING SPOOL @ tivorostanic MoTOR @ FLow ConTROL sPooL e Yinmaaricd sence, rest epee @ BUCKET POSTION VALVE caret cues 8 £13: FLOW ADJUSTMENT VALVE kPa) Waming Light Turns off @ 17-21 3 “Hysraulle #4 Element tates] 72 PS! (496 kPa) © tivorauttc PUMP, Gear Type — Rated 2 @ 2700 RPM @ 1050 PS! {7239 kPa) Hydrostatic #3 2. Hydraulic Pump, 16.2GPM (613 Liming b. Charge Pump, 10.8 GPM (40,9 Limin.) © Auxiliary Hydraulic Pump, 6.9 GPM (26,1 Limin.) . "Relief Valve, 3000 PS! (20685 kPa} © AUXILIARY COUPLER, Case Fluid Drain © AUXILIARY QUICK COUPLERS @ HYDRAULIC CONTROL VALVE © SOLENOID VALVE, . . High Horsepower Controt ‘COUPLER @ PRESSURE SWITCH, Differential 40 PSI {276 kPa) +50 PSI (345 kPa) @ HIGH PRESSURE RELIEF VALVES, 3500 PSI (24133 kPa) 6570916 290) (Sheet 2 Of 2) Piotet n USA. WIRE DIAGRAM LEGEND NO’s COLOR GAUGE 12G OrangelWhite 16 SOR Black 16 SORA Black 16 80S Black 16 5OV Black 16 ‘S4E_ Dk. Green 16 S4EA Dk. Green 16 S4F Dk. Green 16 546 Dk. Green 16 CHECKING & ADJUSTING MAIN RELIEF ‘VALVE (DUAL PRESSURE} 1 2 5. Lilt and Block the loader. Connect the Inydraulic tester 19 the quick couplers @ Disconnect Oona the electrical connectors Start the engine, Chock the main reliet valve @ pressure. ngage the high Now trout switch @ NOTE: If the prossure retiet setting is adjusted, 10. 1k wil offect the standard rolet pressure. Always adjust the high pressura eating fret. f adjustment is needed, loosen the jam aut and adjust the high flow raliet valve pressure by turning in to crease pressure or out to decrease Pressure. The correct setting és 2950-3030 PSt (20340-21030 kPa), Disengage the high flow hydraulics. Stop the ‘engine. tighten the jam nwt to 36 ft-lbs. 447 Neo} torque. Romove the access plug or foosan the jam nut (on the main relief vatve @ - ‘Start the engine. Use an allen wrench end turn the screw in to increase pressure oF out to decrease pressure. The correct setting is 2180-2250 PSI (14824-15514 kPa). Stop the engine. install the access plug or tighten, the fom nut. Disconnect the bydcaulc tester, WIRING DIAGRAM PARTS LEGEND-- [i] Hamess Connector [2 switen [3] Solenoid Connectors mews Wi. check the refet valve In the tydrautic pump @" end section: connect the hydraulic tester into the outlet fine of the pump @* By restricting the flow, with the hydrauilc tester, tho ‘pressure should be 3000 PS! {20685 kPa) at the ‘ollf valve ©. {zee1 ssqwoenies powns) s0czzL9# UAH youey UW Peresedo 1ond YUM) Heyes 02000, pow 204 ee WVUBVIG ONIYIM ONY AMVHO MOT4 ILWLSONGAH / DINVEGAH FF nent HYDRAULIC / HYDROSTATIC SYSTEM OPERATIONS ‘To Be Used With HYDRAULIC / HYDROSTATIC FLOW CHART AND WIRING DIAGRAM For Modet 843H (With Pilot Operated Main Relief) Chart #6722305 (Printed September 1992) CHART LEGEND @ RESERVOIR, Cop:..... 3.5-4.0 Gals. @ HYDRAULIC CONTROL VALVE (13,2-15,1 LY @ ORIFICE, ... 0.024" (0,61 mm) Dia. © SCREEN, 60 Mesh — @ SOLENOID VALVE,. High Horsepower © BREATHER 5 Micron ‘8, Forward Flow Fluid Control (High Flow) @ pirruseR 'b. Reverse Flow Fluid Control (Low Flow) © TEMPERATURE SWITCH,. 225-232°F. @ ANTI-CAVITATION VALVE (100-111°C) @ LOADER CHECK VALVES, . 3 @ COLD FLUID BY-PASS VALVE, 297 PSI @ ORIFICE (2048 kPa) @ MAIN RELIEF VALVE, Pilot Operated @ Port stock ‘Normal Operation; © CHARGE BY-PASS VALVE, 180-200 PSI (2260-2400 PSI (15514-16548 kPa) (1241-1379 kPa) High Flow Control, @ ORIFICE... Motor Case Drain 0.217" 3000 PSt (20685 kPab (5,5 mm) Diameter © PORT RELIEF VALVE,..... 3500 PSI © tvorostaric MoTOR (24133 kPa} @ HYDRAULIC PUMP. Goar Type-Rated © ELECTRICAL SELECTOR VALVE @ 2700 RPM 8, Hydraulic Pump, 16.2 GPM (61,3 Umin.) b. Charge Pump, 10.8 GPM (40,9 Limin.) c. Auxiliary Hydraulic Pump, 6.9 GPM (26,1 Limin.) © PRESSURE SWITCH (Dual Function), Hourmeter Starts @ 19-23 PSI (131-159 kPa); Warning Light Turns Off @ 17-21 PSI (117-145 kPa) @ RELIEF VALVE, 3000 PSI (20685 kPa) @ HIGH PRESSURE RELIEF/REPLENISHING VALVES (4},.. 3500 PSI (24133 kPa) @ HvpRosTaTIC PUMPS AUXILIARY COUPLER,... Case Drain @ AUXILIARY QUICK COUPLERS @ AUXILIARY COUPLERS,....... High Horsepower Flow @ Tur cyunoER @ Ut CYUNDERS @ STEERING SERVO CONTROL 722008 9.92 (Sheet 2 Of 21 @ UN-LOADING SPOOL /PRESS. RELIEF VALVE @ FLOW CONTROL SPOOL @ FLOW ADJUSTMENT VALVE @ CHECK valve © BUCKET POSITION VALVE @FITER,....... Hydraulic #4 Element @ BY-PASS VALVE,... 72 PS! (496 kPa) © on coo“eR © rurer, Hydrostatic #3 Element @ piAGNosmic COUPLER @ PRESSURE SWITCH,..... Differential 40 PSI (276 kPa} 50 PSI (345 kPa) @ BY-PASS VALVE,... Printed in USA. SgRRESEgEE s HEE sseseuerd CHECKING & ADJUSTING MAIN RELIEF ‘VALVE (DUAL PRESSURE) Lift & block the loader. Connect the trydraulic tester to the quick couplers @. All tests are done with engine speed at full RPM, Start the engine. Check main relief vaive pressure. The correct pressure for the low ‘setting is 2250-2400 PSI (16514-16548 kPa}. Engage the “high pressure’’ function & ctieck the high few pressure. The comect pressure for the high setting Is 3000 PSI (20685 kPa). NOTE: if adjustment is necessary , adjust the low pressure setting ‘before adjusting the high pressure setting. 5. Stop the engine. To adjust the tow pregoure on the main relief valve @ , use tthe following procedure: ‘8, Disconnect the pilot hose & remove the adapter fitting. b. Remove the high pressure adjustment housing (item 1) i. © Use a 1/4” allen wrench (Item 2) to tum the adjusting ‘screw (ttem 3) in to increase or out to decrease pressure [A]. One tum is equal to ‘approximately 490 PSI (3379 kPa). 4. Install the high prossure adjustment housing & adapter, Connect the pilot ©. Start the engine and check the Dressure setting. Repeat the procedure until the pressure setting is correct. re » > PARTS LEGEND 6. Whon the tow pressure setting is corect, the next step Is to set the high pressure adjustment of the main relief valve @ use the following procedure: 2 Stop the engine, Disconnect the pilot hose’& remove the adapter. & Use @ 1/4” allen wrench item 1) to pressithe push pin, item 2} in until it bottéms out against the shoulder stop (tem 3) Bi]. Tun the adjusting guide (Item 4) in to increase or out to decrease the pressure [8]. One turn is equal to approximately 390 PSI (2689 kPa). Install the adapter & connect the pilot hose. @ Start the engine. Engage the “high horsepower" function and check for the corfect pressure. Repeat the proceddure until the pressure setting is correct. FLUID FLOW EXPLANATION: Hydraulic fluid flows from the reservoir @ and enters the inlet port of the triple (3 section) gear pump @ . The larger section @ ® of the pump supplies fiow to the inlet of the hydraulic control valve @ . The pump pressure is controlled by the main relief valve @ . The controt valve @ is a four-section, open center, closed port, series type valve. When all four spools are eae position, the ftuid goes through the control valve @ and to the hydraulic finer @ . ‘When the lift arms are raised, the hydraulic pump @ @ fluid flow is directed to the ba: end of the lift cylinders @ . The fluid from the rod end of the lift cylinders @ returns to ‘the bucket position valve€® and is directed to the center of the flow-control spool @ . The flow-control spool @ and flow adjustment valve ® direct this flow. A percentage of the fluid is directed over the flow adjustment valve @ to position the bucket. The rest of the fluid is directed through the orifice in the flow-control spool @ and onto the return port of the control valve @ lift section). ‘The fluid flow from the flow-control spot @ and flow adjustment valve @ are ageinst the un-oading spool/pressure relief valve @. The un-oading spool/pressure relief vaive @ moves to allow extension of the tit cylinder @ as the lift cylinders @ raise the lift arms. ‘The unloading spool/pressure relief valve @ is to relief fluid from the base end of the tilt cylinder © if the bucket is fully rolled out and the lift cylinders @ are still extending. ‘The fluid from the charge pump @ © flows to the four-way cross fitting and is called “charge pressure fluid”. The fluid flows to the oil cooler @ or oil cooler by-pass valve @ . The oil cooler by-pass valve @ will open when the fluid temperature is cold or if there is excessive fluid pressure. The fluid flows through the oil cooler @ , then through the hydrostatic fitter @ and pest the pressure switch @ to supply the front and rear hydrostatic pump @ with charge pressure and on to the charge by-pass valve @. The pressure switch @ has 2 dual function, it starts the hourmeter and turns the warning light off. The charge pressure fluid flows into each pump @ and mator © to cool, lubricate and replenish ‘the fluid supply which has been lost through case drain. Also fluid from the four-way cross fitting supplies fluid to actuate the steering servo controls @ and the electrical solenoids @ for high horsepower operation. The return fluid from the steering servo controls @ and electrical solenoids @ flows to the port block @ There are two hydrostatic pumps © and two hydrostatic motors ®@ . One pump and one motor work together 8s 8 pair to drive one side of the loader. The other pump and motor work as 8 pair to drive the opposite side of the loader. ‘The swash plates of the hydrostatic pumps @ are angled by the steering servo controts @ in either direction, the pumps @ force fluid, under pressure, to the motors © . ‘The motors @ tum and push the tow pressure fluid back to the pumps @ to be used again. The motors @ contain a shuttle valve which allows some fluid from the drive loop to go to the port block @ and back to the reservoir @ . The hydrostatic pumps @ contein four high pressure reliefireplenishing valves @ . There are two valves @® for drive on each side of the loader: one for forward travel and one for reverse travel. The high pressure relief/replenishing valves ® have a dual function. The valve cartridges @ are pushed off their seats to allow fluid flow from the charge loop to cool, lubricate and replenish the pumps @ and motors @ . in forward or reverse (wiien the swash plates are angled), the fivid has a higher pressure the charge fluid. This pressure difference forces the high pressure replenishing valve @ onto the seat. The high pressure replenishing vaive @ will open allowing the drive pressure to relieve into the charge loop to be used again. if excessive pressure is generated by the pumps-@ . Excess charge pressure fluid which is relleved over the charge by-pass valve @ goes through the port block @ and joins the hydrostatic motors @ case drain and flows to the reservoir ‘through the diffuser @ . Fluid from the cold oil by-pass valve @ flows into the port block @ and back to the reservoir @ under conditions of cold fluid or excess flow. The hydraulic filter @ has a by-pass vaive @ to protect the system if the filter element becomes plugged. The hydrostatic filter @ has a by-pass valve @ to protect the system If the filter element becomes plugged and a pressure differential switch @ which indicates the condition of the filter element. ‘The diagnostic coupler @ provides a quick access for checking the charge pressure in the system. HIGH FLOW OPERATION ‘Taming the switch [2] “ON” for high flow operation will activate the following functions: twill energize the electrical solenoid @ @, and the electrical selector valve @ . When the electrical solenoid @ ® is energized the charge pressure will shift the control valve spool @ to allow the fluid flow from the hydraulic pump @ ® to flow to the setector valve @ where the fluid joins with the fluid from the auxiliary hydraulic pump @ ©. This fluid than flows to the high flow quick coupler @ at the front of the loader. The retum. fluid flows to the control valve @ end to the hydraulic fitter @ . Case drain fluid (Example: Planer) will return through the coupler @ and back to the port block @ to join the fiuid going to the reservoir @. When the high flow operation is engaged; it wil engage the pilot operated main reliof valve @ which will increase the relief pressure to 3000 PS! (20685 kPa). The rolief in the auxiliary hydraulic pump @ ¢ and main relief vatve @ will open to relieve excessive pressure. ‘The fluid from the auxiliary hydraulic pump @ © when not in use, flows to the electrical salector valve @ and returns to the hydraulic fitter @ . ‘Turning the switch [2] “REV” for reverse operation will active the electrical solenoid @ and shift the control valve spoa! @ to allow fluid flow from the hydraulic pump @ 2 to flow to the high ftow coupler @ . The retum fluid goes to the control valve @ and to the hydraulic filter @ . The electrical selector valve @ is not energized in this function. ail null cal at 0988 For Model, 843H (S/N 60450 & Above) 967: Chet /20945 (Printed Soptember 1991) HYDRAULIC / HYDROSTATIC FLOW CHART AND WIRING DIAGRAM x bobcat HYDRAULIC / HYDROSTATIC SYSTEM OPERATIONS ‘To Be Used With HYDRAULIC / HYDROSTATIC FLOW CHART AND WIRING DIAGRAM For Modet 7 843H (S/N 50450 & Above) ‘Chart #6720945 (Printed September 1991) ee CHART LEGEND - 3.5-4.0 Gals. (100-111°C) @ COLD FLUID BY-PASS VALVE, 297 PSI (2048 kPa} @ Fort BLocK © CHARGE BY-PASS VALVE, 180-200 PS! (1241-1379 kPa) @ ORIFICE... Motor Case Drain 0.217" {6,6 mm} Diameter @ HvoRostariC MOTOR @ HYDRAULIC PUMP,. Gear Type-Rated @ 2700 RPM a. Hydrouilic Pump, 18.2 GPM (61,3 Limin.) 'b, Charge Pump, 10.8 GPM (40,9 L/min) Ausilisry Hydraufic Pump, 6.9 GPM (26,1 Limin.) @ PRESSURE SWITCH (Dual Function), Hourmeter Starts @ 19-23 PSI {131-159 kPa); Warning Light Tums Off @ 17-21 PSI (117-145 kPa) © RELIEF VALVE, 3000 PSI (20685 kPa) © HIGH PRESSURE RELIEF/REPLENISHING VALVES (4)... 3500 PSI (24133 kPa) @ HybROsTATIC PUMPS. @ AUXILIARY COUPLER... Case Drain @ auxtuary quick COUPLERS @ auxwiary COUPLERS,....... High Horsepower Flow @ mur cyunvER @ UFT CYLINDERS @ STEERING SERVO CONTROL 720m 8 {sheet 2 0 2) @ HYDRAULIC CONTROL VALVE @ ORIFICE, ... 0.024” (0,61 mm) Dia. @ SOLENOID VALVE,. High Horsepower ‘2. Forward Flow Fluid Control (High Flow) b. Reverse Flow Fluid Control {Low Flow) @ ANTLCAVITATION VALVE @ LOADER CHECK VALVES,........ 3 @ ORIFICE © MAIN RELIEF VALVE, (Electrical Controtied} Normal Operation; 2200-2300 PSI (15159-15859 kPa} High Flow Control; 3000 PSI (20685 kPa) @ PORT RELIEF VALVE,..... 3500 PSI (24133 kPa) @ ELECTRICAL SELECTOR VALVE @ UN-LOADING SPOOL/PRESS. RELIEF ‘VALVE @ FLOW CONTROL SPOOL @ FLOW ADJUSTMENT VALVE @ BUCKET POSITION VALVE @ FULTER,......- Hydraulic #4 Element « 72 PSI (496 kPa) @ om cooteR © Furer,..... Hydrostatic #3 Element @ DIAGNOSTIC COUPLER @ PRESSURE SWITCH,..... Differential 40 PS! (276 kPa} @ BY-PASS VALVE,... 50 PSI (345 kPa) Prog i USA. WIRE LEGEND NO's COLOR 12GA— OrangelWhite SOR Black BORA Black 50S Black SOV Black sow Black S4E Dk. Green S4EA Ok. Green S4EB Lt, GreeniYellow S4F Dk. Green 54G Dk. Green 1. Lift & block the loader. 2. Connect the hydraulic tester to the quick coupters @ . » Disconnect the electrical connectors EP ond EA”. 4. Start the engine. Check the main rellef valve @ pressure. 5. Engage the high flow hydraulic system NOTE: If the high pressure retiof setting is adjusted, it will effect the standard relief pressure. Always adjust the high pressure setting first. 6. if adjustment is needed, loosen the jam ‘nut and adjust the high flow relief valve pressure by turning in to increase Pressure or out to decrease pressure The correct setting is 2960-3050 PSI (20340-21030 kPa). 7. Disengage the Kigh flow hydraulics. Stop the engine. Tighten the jam nut to 36 ft- lbs. (47 Nm) torque. 8. Remove the access plug or loosen the jam nut on the main relief valve @ . 9. Start the engine. Use an allen wranch and ‘turn the screw in to increase or out to decrease pressure. The correct setting is. 2150-2250 PSI (14824-16514 kPa). PARTS LEGEND Hamess Connector — ‘Solénoid Connectors a. Forward Fluid Flow b. Reverse Fluid Flew (Ty if Ula 10. Stop the engine. Install the access plug ‘or tighten the jam nut. Disconnect the hydraulic tester. Tl. To check the relief valve @ in tho hydraulic pump end section: connect the hydraulic tester into the outlet of the pump @ ©. By restricting the flow, with the hydraulic tester, the pressure should be 3000 PSI (20685 kPa} at the relief valve @ . == FLUID FLOW EXPLANATIONS==—-=— Hydraulic fluid flows from the reservoir @ and enters the inlet part of the triple {3 section) gear pump @ . The larger section @ ® of the pump supplies flow to the inlet of the hydraulic control valve @ . The pump pressure is controlled by the main relief valve @ . The control valve @ is a four-section, open center, closed port, series type valve. When alll four spools are in neutral position, the fluid goes through the control valve @ and to the hydraulic filter @ . When the lift arms are raised, the hydraulic pump @ @ fluid flow is directed to the base ‘end of the lift cylinders @ . The fluid from the rod end of the lift cylinders @ returns to the bucket position valve@® and is directed to the center of the flow-control spool @ . The flow-contol spoot @ and flow adjustment valve @ direct this flow. A percentage of the fluid is directed over the flow adjustment vaive @ to position the bucket. The rest of the fluid is directed through the orifice in the flow-control spool @ and onto the return port of the control valve @ (lift section). The fluid flow from the flow-control spool @ end flow adjustment valve @ are against the un-toading spoolipressure relief valve @. The un-loading spoolipressure relief vaive @ moves to allow extension of the tilt cylinder @ as the lift cylinders @ raise the lift arms. ‘The un-loading spoolipressure relief valve @ is to relief fluid from the base end of the tilt, cylinder @ if the bucket is fully rolled out and the lift cylinders @ are still extending. ‘The fluid from the charge pump @ © flows to the four-way cross fitting and is called “charge Pressure fluid”. The fluid flows to the oil cooler @ or oi cooler by-pass valve @ . The oil cooler by-pass valve @ will open when the fluid temperature is cold or if there is excessive fluid pressure. The fluid flows through the oil cooler @ , then through the hydrastatic filter @ and past the pressure switch @ to supply the front and rear hydrostatic pump @ with charge pressure and on to the charge by-pass valve @. The pressure switch @ has a dual function, it starts the hourmeter and turns the warning light off. The charge pressure fluid flows into each pump @ and motor @ to cool, lubricate and replenish the fluid supply which has boen lost through case drain. Also fluid from the four-way cross. fitting supplies fluid to actuate the steering servo controls @ and the electrical solenoids @ for high horsepower operation. The return fluid from the steering servo controls @ and electrical solenoids @ flows to the port block @. ‘There are two hydrostatic pumps © and two hydrostatic motors @ . One pump and one motor work together as a pair to drive one side of the loader. The other pump and motor work as a pair to drive the opposite side of the loader. The swash plates of the hydrostatic pumps @ are angled by the steering servo controls @ in either direction, the pumps @ force fluid, under pressure, to the motors @ The motors @ tum and push the low pressure fluid back to the pumps @ to be used again. The motors @ contain a shuttle valve which allows same fluid from the drive loop to go to the port block @ and back to the reservoir @ . The hydrostatic pumps ® contain four high pressure relief/replenishing vatves © . There are two valves @ for drive on each side of the loader: one for forward travel and one for reverse travel. The high pressure felietireptenishing valves @ have a dual function. The valve cartridges @ are pushed off their seats to allow fluid flow from the charge loap to cool, lubricate and replenish the pumps © and motors @ . In forward or reverse (when the swash plates are angled), the fluid has a higher pressure the charge fluid. This pressure differance forces the high pressure replenishing valve @ onto the seat. The high pressure replenishing valve @ will open atlowing the drive pressure to relieve into the charge loop to be used again if excessive pressure is generated by the pumps ® Excess charge pressure fluid which is relieved over the charge by-pass valve @ goes through the port block @ and joins the hydrostatic motors @ case drain and flows to the reservoir ‘through the diffuser @ . Fluid from the cold oil by-pass valve @ flows into the port block @ and back to the reservoir @ under conditions of cold fluid or excess flow. The hydraulic filter @ has a by-pass valve @ to protect the system if the filter element becomes plugged. The hydrostatic fitter @ has a by-pass valve @ to protect the system if the filter elément becomes plugged and a pressure differential switch @ which indicates the condition of the fitter element. ‘The diagnostic coupler @ provides:a quick access for checking the charge pressure in the system. : HIGH FLOW OPERATION ‘Turning the switch IE “ON” for high flow operation will activate the following functions: ie will energize the electrical solenoid @ 8, the main relief valve @ and the electrical selector valve ® . When the electrical solenoid @ ®is energized the charge pressure will shift the control valve spool @to allow the fluid flow from the hydraulic pump @ ® to flow to the electrical selector valve @ where the fluid joins with the fluid from the auxiliary hydraulic pump @ ©. This fluid than flows to the high flow quick coupler @ at the front of the loader. ‘The rétun fluid flows to the control valve @ and to the hydraulic filter @ . Case drain ‘fluid (Example: Planer) will return through the coupler @ and back to the port block @ to join the fluid going to the reservoir @ . ‘When the high flow operation is engaged; it also energized the main relief vaive @ which ‘will Increase the relief pressure to 3000 PSI (20685 kPa). The relist valve @ in the auxiliary hydroulic pump @ ¢ and main reliet valve ® will open to relieve excessive pressure. ‘The fluid from the auxiliary hydraulic pump @¢ when not in use, flows to the electrical selector valve @ and returns to the hydraulic filter ‘Turning the switch El "REV" for réverse operation wil active the electrical solenoid @ b and shitt the control valve spool @ to allow fiuid flow from the hydraulic pump @ 8 to flow to the high flow coupler @ . The retum fluid goes to the control valve @ and to the hydraulic filter @ . The electrical selector valve @ and the main relief valve @ are not energized in this function. 2 moupruvonneaymena -30KYUO “1 EE) (2661 sequerdes peumen sasozco# vee —-YODQOQ, iS aera ae mtg eas ne SS oon 4 Sas roeeid at =e AUVHO MOTI DUMISONGAH / TINVEGAH eo eo o FE oct HYDRAULIC / HYDROSTATIC SYSTEM OPERATION ‘Yo Bo Used With HYDRAULIC / HYDROSTATIC FLOW CHART For Model 8438 (Chart #6720555 (Printed September 1892) CHART LEGEND BREATHER CAP, 5 Micron @ FLOW CONTROL SPOOL @ SCREEN, + 100 Mesh @ FLOW ADJUSTMENT VALVE @ ReEseRvoIR, Capacity @ CHECK VALVE 35-40 Gals. (13,2-15.1 L) @ BUCKET POSITION VALVE (0PT.) © veruser @ HYDRAULIC FUTER, ..... 10 Micron © TEMPERATURE SWITCH, 225-232°F. @ BY-PASS, VALVE, .. 72 PSI (496 kPa! {108-1119 C)_— @ HYDROSTATIC FILTER, .. #3 Element @ COLD FLUID BY-PASS VALVE, @ DIAGNOSTIC COUPLER 297 PSI (2048 kPa) @ DIFFERENTIAL PRESSURE SWITCH, 3 PORT SLCk es a 40 PSI (276 kPa) CHARGE BY-PASS VALVE, .. 50 PSI (345 kPa} ‘10 PSI (758 kPs) $ on Sona 7 @ontrice, ........ Motor Case Drain 0.217" (6,6 mm} @ HYDROSTATIC PUMPS @ xyorostaric moToR @ PRESSURE SWITCH (Dual Function) Hourmeter Starts @ 19-23 PSI (131-159 kPal; Waming Light Tums Off @ 17-21 PS} (117-145 kPal @ HYDRAULIC PUMP, ..... Gear Type Rated @ 2700 RPM & 1050 PS! (7239 kPa) ‘8. Charge Pump, 11.5 GPM (43,5 Limin) Hydraulic Purp, 16.1 GPM (60,9) Limin.) @ Tur CYLINDER @ wrt cyuinpers AUXILIARY QUICK COUPLERS (OPT.) @ LOAD CHECK VALVES (3) @ ANTI-CAVITATION vatve @ HYDRAULIC CONTROL VALVE @ onirice @ MAIN RELIEF VALVE, 2260-2400 PSI (15514-16558 kPa) @ PORT RELIEF VALVE, 3500 PSI (24133 kPa) @ UN-LOADING SPOOL/PRESSURE RELIEF VALVE 7208s 9221 (Sheet 2 Of 2) @ HIGH PRESSURE/REPLENISHING RELIEF VALVES, .... 3500 PSI (24133 kPa) Pred USA, 2 FLUID FLOW EXPLANATION: Hydraulic fluid flows from the reservoir @ to the infét port of the tandem (2 section) gear eump @ . The larger section @ of the hydraulic pump supplies pressure to the inlet of ‘the hydraulic control valve @ . The pump pressure is cantrojled by the main reliet valve @ . ‘The control valve @ is a three-section, open center, closed port, series type'vaive. When all three spools are in neutral! position, the fluid goes through the control valve @ to the hydraulic fitter @ If one of the spools is activated, the fluid goes out the respective port to either the base end, or the rod end of the cylinderts) @ ®. As the fluid goes into one end of the cylinder{s) © @ the fluid from the other side of the cylinder flows back into the controt valve @ . ALSO SEE BUCKET POSITIONING SYSTEM OPERATION {OPTIONAL}. ‘When the cylinder(s) ® @ reach the end of the stroke, the fluid reaches the setting of the main relief valve @ , it will open and let the fluid by-pass the hydraulic circuit (internally) and go beck to the reservoir @ . ‘The fluid flows from the charge pump @" to either the oil cooler @ or the cooler by-pass valve @ which will open when there is cold fluid or if there is excessive fluid pressure. The fluid flows through the oit cooler @ , then through the hydrostatic fitter @ and into the four-way block. The fluid flows past the pressure’ switch @ to the charge by-pass vatve @ . The pressure switch @ has a dual function, it starts the hourmeter and tums the waming light “OFF”. Normal flow of fluid is through the four-way block to the front end rear hydrostatic pumps @. This fluid flow is called “charge pressure” and supplies the hydrostatic pumps @ and hydrostatic motors (® with charge fluid. The charge fluid is used by the pumps and motors, but as the charge pressure increases, the charge by-pass vatve @ will open to prevent excessive pressure build-up. ‘The charge fluid flows into each pump @ and motor @ to cool, lubricate and replenish ‘the fluid supply which is lost through case drain. Case drain from the pumps @ flows into the inlet side of the hydraulic pump @ through intemal porting. ‘There are two hydrostatic pumps @ and motors @ . One pump and one motor work ‘together as 2 pair to drive one side of the loader. The other pump ‘and motor work as a air to drive the opposite side of the loader. The swastiplates of the hydrostatic pumps @ sre angled to either direction, the pumps @ force fluid, under pressure, to the motors ® . The motors @ tum and push the Jow pressure fluid back to the pumps @ to be used ayjain. Tha motors @ contain a shuttle valve which allows some fluid from the “drive loop’ to go to the port black @ and back to the reservoir @ . ‘The hydrostatic pumps @ contain four high pressure reliefireplenishing valves @ . There ‘are two valves @ for drive on each side of the loader: one for forward travel and one for ‘reverse travel. The high pressure relief/replenishing valves €® have.a dual function. Inneutral the valve cartridges @ are pushed off their seats to allow fluid flow from the charge loop ‘to coot, lubricate and replenish the pumps @ and motors @ . in forward or reverse travel, the fluid has a higher pressure than charge pressure fluid. This pressure difference forces ‘one of the high pressure replenishing valves @ against the seat. The high pressure replenishing valves @ also act as a high pressure relief valve for the pumps @ . The high pressure replenishing valves @ will open allowing the “drive pressure” to relieve into the charge loop to be used again if excessive pressure is generated by the pumps @. Excess change pressure fluid which is relieved over the change by-pass valve @ goes through the port block @ and joins the hydrostatic motors @ case drain fluid and flows to the reservoir @ through the defuser @ . Fluid from the cold fluid by-pass valve @ flows into ‘the port block @ and back to the reservoir @ . Both the hydraulic filter @ and hydrostatic filter @ have a by-pass © @ . The hydrostatic fiker @ also has a pressure differential switch @ which indicates the condition of the filter. ‘The diagnostic coupler @ provides a quick access for checking the cherge pressure. BUCKET POSITIONING SYSTEM OPERATION (OPTIONAL) ‘The lift and tilt section of the control vaive @ work together to position the bucket as. the lift arms are being raised. When the lift arms ere being raised, the hydraulic pump @* flow is directed to the base end of the lift cylinders @ . The fiuid from the rod end of the lift cylinders @ returns to the bucket position valve @ and is directed to the center of the flow-contro! spoo! @ . The flow-controt spoo! @ has an orifice at each end. ‘Some of the fluid flow is directed to the base end of the tilt cylinder @ and the other portion Of the fluid is directed through the opposite end of the flow-contra! spoo! @ to the return port of the lift section of the contro! valve @ The fluid flow from the flow-control spoo! @ is against the un-loading spool @ and flow adjustment vatve @ . An increase in fluid pressure causes the flow adjustment valve @ to ‘open which allows the flow of the fluid to the base end of the tilt cylinder © . The fluld trom the rod end of the titt cylinder @ is contained by the un-toading spool @ and allows the rod end fiuid to retum into the control valve @ . The pressure reliof valve @ is to relief fluid from the base end of the tilt cylinder @ if the bucket is fully rolled out and the lift cylinders @ are still being extended. 2 HYDRAULIC SYSTEM TROUBLESHOOTING ‘The following troubleshooting chart is provided os an assistance in locating and correcting problems which are most common. Many of the recommended procedures ‘must be done by authorized Bobcat Service Personnel only. ‘The hydraulic system will not operate. 142,34 ‘Slow hydraulic system action. 13,567 Hydraulic action is not smooth. 1,5,6,7,8 Lift arms go up slowly at full engine RPM. 1,3, 5,6, 7,9, 10, 1 ‘The lift arms or BobTach will move with the pedal in neutral position. 5, 10 The lift arms come down with the pedal in the neutral position. 5, 11, 12, 13, 14 The bucket does not self-level. 16, 16, 17 ‘The bucket will partially selfevel. 15, 16 ‘The bucket as no power to roll forward. v7 ‘The bucket does not roll back. KEY TO CORRECT THE CAUSE 1. The fluid level is not correct. 2. The pedal linkage is disconnected. 3. The hydraulic pump has a defect. 4. The relief valve has a defect. 5. The pedal linkage is not adjusted correctly. 6. Relief valve is not at the correct pressure. 7. Suction leak on the inlet side of the hydraulic pump. 8 Flui 9. Using the loader for more than its rated capacity. 10. Spool in the valve section is not centering or the centering spring is broken. 11, Internal leak at the lft eylinder(s). 12, External leak at the lift cylinder(s). 13. Port relief seat is leaking. 14. Load check has a defect in the valve section. 15. Check the flow divider. 16. Check the unloading spool. 17. Check the self-level r is cold. 843 Loader 2 Service Manual c HYDRAULIC SYSTEM INFORMATION ae or as Amr ‘Aways keep craic and hydrostatic parts clean. Cian outs ool asamse before bagning ropa. ‘se pgs an cape fo cover open ports. Dit can acy famege te system. taezto2se Flare Connections Use the folowing procedure to tighten the flare fting: ‘Tighten the nut until it makes contact with the seat ‘Make a mark across the “flats” of both the male and femah ports of the connection Use the chart to find the corect tightness needed (5) It the fitting leaks after tightening, disconnect it and inspect the seat area for damage. ‘Straight Tiwead Oving Fiting ‘When instaling this fiting, the O-ring must be first lubricated. Loosen the jam nut, ital the fing ito place, then tighten the Jom nut. Tighten the jam nut until and the washer ar tight against the surface ‘Tubelines and Hoses Moke replacement of tubelines which are bent or have become flat. There wil be 2 restriction of fluid flow, which will give @ slow hydraulic action and cause heat. Make replacement of hoses which show signs of wear, damage or weather cracked rubber ‘When instaling tubelines or hoses, make sure you use two wrenches when loosening and tighten them. A ‘Mark @ Line an Nut Flats of Both Nuts ‘Tighten to Correct ‘Amount from Chart B ‘ube Sze Rotate No. Tarnch Sica | Oued Oa,| Thandie | of Hex Fate wer | ener | u-20 | 242 we | ser [ones [2 me] ve | aes |? r se | ew | tve-8 te [we fone | vaer |r vane re [ aa z vse" -7a [a4 ag ve" 2 | V2-38 c anes 943 Loader ‘Service Manual LUFT CYLINDER [Checking the Litt Cyinderts Lower the lit arms. Stop the engine. Activate the lift pedal to release the hydraulic pressure Disconnect the hose from the tubeline which comes from the bbese end ofthe lft cylinder (ight aide) A] (et side) (8). Only check one cylinder at @ time Put # plug in the tubetine 3802 Diesel fuel or hydraulic fluid under pressure can penetrate skin or eyes causing serious injry. Fld leaks ‘Under pressure may not be visible. Use a piece of cardboard or wood to find leaks. Do not use your bare hhand. Wear safety goggles. If hid enters skin or eyes, ‘Get immediate medical attention. waorea Remove Hose from ‘Base End of itt Cylinder ‘Start the engine and push the top (toe) ofthe lift pedal. f there ry leakage from the open hase remove the cyinder fo repait. Repeat this procedure to check the ift eyinder on the other sie. Removal and Inctaltation Raise the Itt arms. Install jackstands under the BobTach. Stop the engine. Activate the ift pedal to release the fnydrauic pressure Remove the lock bolt st the rod end of the cylinder Installation: Tighten the lock bolt 10 8-10 fabs. (1114 Nm} torque, Remove the rod end pin 23. 843 Loader ‘Service Manual Cc FT CYLINDER (Cont'd) Remove the lock bolt at the base end pivot pin. Remove the base end pivot pin i 24998 ‘Sige the cylinder forward a small amount. Disconnect the hoses, fom the eylinaer (I. Remove the lift cylinder from the loader. ‘See Page 213 for Hydraulic Cylinder Repair Cc e301 1843 Loader 28 Servien Manat ‘Tur CYLINDER Checking the Tit Cylinder Remove the bucket. Roll the Bob ach fully backward, Stop the ‘engine. Activate the tit pedal to relesse the hydraulic pressure. Disconnect the hose which goes to the base end of the tit cvinder Put a plug in the hose PINT (ey Diesel fuel or hydraulic fluid under pressure can ‘penetrate skin or eyes causing serious injury. Fuld leaks Under pressure moy not be visible. Use a piece of ‘cardboard or wood to find leaks. Do not use your bare, ‘hand. Wear safety gogoles. H fui enters akin or eves, ‘et immediate medical attention. w207e-1205 Start the engine and push the bettom thee!) of the tt pod i for repat. leakage from the open port, remove the tit linger Removal and Installation Remove the bucket or attachment. Roll the BobTach fully forward. Stop the engine. Push the tit pedal to release the hydraulic pressure. Disconnect the hoses at the tit eylinder Remove the lock bolt atthe rod end pin 3). Intallation: Tighten the lock bolt to 8:10 ft-lbs. {1114 Nm) Remove the rod end pin Cc ‘TUT CYLINDER (Cont'd) Remove the lock bolt at the base end pin (A). Remove the pin at the base end of the ttt cylinder Remove the tit cylinder from the loader. See Page 2-7 forthe Cessne tit cylinder and Page 2~18 for ‘ll the other tk cylinders. Use two pieces of shim stock, to install the rod end of the cylinder, so there is no damage to the seals, ‘TUT CYLINDER (CESSNA) “The tool listed will be needed to do the following procedure: MEL1074 ~ Oving Seal Hook MEL-1033 — Rod Seal Installation Too! MEL-1075 — Gland Nut Wrench MEL1010 — Seal Installation Too! Disassembly NOTE: If there is movement between the head and the snap ring the complete cylinder must be replaced. Put the base end of the cylinder in @ drain pan. Move the rod in and out to remove the fild from the eylinder barrel. Put the bas fend of tha cylinder in a vise. Put 9 c0p on the fting (Rem 1) inthe end cap Lift the retainer ring (item 2) out of the cylinder baret i Put e wrench on the fitting and tum the end cap ‘counterclockwise to remove the retainer ring Remove the cylinder end cap, piston and rod assembly from the cylinder barrel Pur the rod end of the ron 2 vise. Remove the piston from the rod 843 Lander Service Manual THT CYLINDER (CESSNA) (Contd) A Remove the O-ring from the end of the rod Remove the cushion sleeve from the rod Remove the end cap from the rod, e.ss02 Remove the wiper seat (6). B Remove the oil sea! Cc easn {tem 1) and back-up washer Item 2) from Remove the the end cap TUT CYLINDER (CESSNA) (Cont) Assembly ‘Remove the teflon seal and the O-ring from the piston (A) Wash all the parts In clean solvent. Ory with air only. Destroy old seals and O-rings. Install the piston on the toot Inetal the O-ing on the piston using the toot i Install the teflon seal over the tool and on the piston f). NOTE: To prevent damage tothe teflon seal, donot tum itinto the piston groove. Install the piston into the tapered end ofthe too! to get the teflon seal to piston size diameter. 8.2673 Instat the oll seal inthe end cap be (043 Loader ‘Service Menust Cc ‘TILT CYLINDER (CESSNA) (Cond) Inetal the wiper seal, withthe lip toward the outside ofthe ond cao Bl. instal the backup washer (em 1) and Orxing tem 21 on the end cap Cc 2.008 4 Put oil on the oll and wiper seal and install on the rod [5 c installthe cushion sleeve, with tapered end towers the end cap Install the O-ring on the end of the rod. Remove the piston from the tool Install the piston on the shaft, with the recessed edge toward the O-ing © 83902 8.3015 ‘843 Loader Service Manual 2-10. ‘TIT CYLINDER (CESSNA) (Cont's) “Tighten the piston to 400-485 f-tbs. (542-617 Nm) torque Lubricate the teflon seat and O-ring. Install the piston into the cylinder barel and work the teflon seal and Oring past the slot in the barrel ‘nstall the rod and end cap assembly into the cylinder bart Install the end cap into the barrel, work the O-ring past the slot Rotate the end cap until the small hole in the end cap can be s300n in the sot. 2-480 2.804 ‘849 Loader Service Manuat ‘TIT CYLINDER (CESSNA) (Cont'd) Install the new retainer ring hook end (tem 1) nto the hole ia Until the retainer ings in the slot. 0.2606 Push down on the retainer ring and make sure itis seated comectly, Push the cylinder rod in and out the full length. Mt must travel freely through the ful stroke, 2-12. 02019 843 Loader Service Menus HYDRAULIC CYLINDER REPAIR NOTE: The following procedure can be used forthe lit and ‘tt oylinders. Disassembly “The tool fisted willbe needed to do the following procedure: IMEL-1074 — O-ing Seat Hook 'MEL-1033 — Rod Seal instalation Too! [MEL1075 — Gland Not Wrench [MEL1216 — Seal Installation Too! MELNT8 — Seal Installation Tool Pur the base end of the cylinder in a drain pan. Move the rod in and out t0 remove the fluid from the cylinder barrel Pu the base end of the cylinder in vise. Remove the end cap {om the from the cylinder using the special too! ‘Remove the rod with the end cap and piston from the cylinder barrel. Put the rod end ofthe shaft in the vise and remove the nut Remove the piston trom the rod 2.3689 Remove the end cap from the rod 213. 843 Loader Service Manual HYDRAULIC CYLINDER REPAIR (Cont'd) Remove the O-ring and back-up washer from the end cep (i). Rernove the wiper seal from the end cap i). Remove the oll seal from the end cap Remove the tetion seal and Oxing from the piston (B)- In clean solvent. Dry with sir only. Destroy 2.0609 ae (043 Loader Service Manual HYDRAULIC CYLINDER REPAIR (Cont'd) A ‘Assembly Inspect the pars for scratches, nicks, bent, etc: Replace the pans as needed. Install the piston on the toot Install the O-ing on the piston using the too!

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