521E - 621E

5B - BRAKE / COOLING

CONTENT

Page

DESCRIPTION 2

BRAKE CIRCUIT 3

COOLING FAN CIRCUIT 6

VARIABLE SPEED FAN VALVE 7

THERMAL BY-PASS 10

PARKING BRAKE 11

SERVICE BRAKE 12

1
7B - BRAKE / COOLING 521E - 621E

BRAKE SYSTEM

The 521 & 621E Wheel Loader Brake system consists of a gear pump (34) mounted to the PTO of the engine at
the RH rear side of the machine. From the brake pump, oil flows to the brake valve (23) mounted to the under-
side of the cab. There are two accumulators (25) (32), in the brake system to store pressurized oil to maintain
braking for a short time after the engine is off. The front and rear brakes draw oil from the accumulators when they
are applied. The control spools for the front and rear brake actuators are part of the brake valve assembly. The
brake valve (23) keeps the accumulators (25) (32) charged when the engine is running. The parking brake (22)
is spring applied and requires hydraulic pressure to release. The parking brake release solenoid (23d) is part of
the brake valve assembly. An accumulator (24) is installed in the parking brake release circuit to assure that it
remains released.

The brake actuators (21) (18) are located at each end of both the front and rear axles.

Brake pump flow (not required to keep the brake accumulators charged), flows to the inlet of the cooling fan drive
motor (35). The cooling fan is located at the rear of the cooling system module between the cab and the engine.
The cooling fan system can be equipped with an optional fan reverser valve (39) to reverse the air flow through the
radiator and coolers to clear debris. The fan reverser valve is manualy activated by a switch in the right console
of the cab or every 30 mn if AUTO mode is selected. In AUTO mode, the speed of the fan is controled by the AIC
depending on the temperature values of engine coolant, air intake, hydraulic oil and transmission oil.

Return oil from the cooling fan drive motor flows through the oil cooler (38) and then to the hydraulic filter (4).

29 Declutch pressure switch

23
4 Return filter
18 Front brakes
19 Rear service brake test fitting
20 Front service brake test fitting
21 Rear brakes
22 Parking brake actuator
23 Brake valve
24 Parking brake accumulateur
25 Brake accumulator
26 Accumulator pressure test fitting
27 Redundant brake pressure switch (62b)
28 rake pressure Alarm switch (103b - 128b)
29 Declutch pressure switch (adustable 1 turn = 4 b)
30 Stop light pressure switch (4.1b)
31 Redundant brake pressure switch (62b)
32 Brake accumulator
33 Accumulator pressure test fitting
34 Brake and cooling pump
521E : 14 Cm3
621E : 23 Cm3
35 Fan drive motor
521E : 14 Cm3
621E : 23 Cm3
37 Thermal by-pass
38 Cooler
39 Fan reversing variable speed control valve 29

2
521E - 621E 5B - BRAKE / COOLING

BRAKE CIRCUIT AND COOLING

24 26 25 32
33

0.16l .8 l
97b 55b
5 23
7 8
4 6
8b rising
22 6b 103b falling

0.3
 0.65

19

 20
21 18
cut-in 57b
cut-out 193b
90 b
3
29

4b 20

88 b
33

8 19 6b
3

30 4.b 3 .8 l
55b

37
37 39

TANK
M1

38
34b
38 35

39
IN
M2
34

4 34

3
5B - BRAKE / COOLING 521E - 621E
BRAKE SYSTEM DESCRIPTION

A gear type hydraulic pump (34), driven by the engine supplies the brake, cooling fan drive and hydraulic cooler
circuit . This pump is mounted onto the PTO of the engine.

The brake valve and accumulator charging valve (23) is a single valve assembly that incorporates the brake accu-
mulator charging function, parking brake actuation and the service brake treadle valves into one assembly.

Oil from the brake pump is supplied to the P port of the brake valve (23). This oil is available to both the priority
valve (23a) and the accumulator charging spools (23b). The accumulator charging spool (23b) is a single spool
that controls both the cut-in and cut-out pressures with a single adjustment. These spools control the state of
charge of both of the brake system accumulators. Upon initial start-up, both the priority valve and the accumu-
lator charging spools are in the activated, or spring based positions. This will cause valve inlet pressure to be
ported to the spring end of the priority valve spool (23a), holding it in the spring based position. This will cause
the priority valve spool (23a) to restrict the inlet flow of the brake valve which will, in turn, charge the accumulators
to the maximum cut-out pressure. Once the cut-out pressure is reached, the accumulator charging spool (23b)
will vent the pilot pressure to the spring end of priority valve spool (23a) , which will then allow priority valve spool
to divert the brake pump flow to the cooling fan drive circuit with minimal restriction. The accumulator charging
spool is held in the cut-out position until the accumulator pressure reduces to the cut-in pressure.

To actuate the brakes, the brake system draws pressurized oil from the accumulators until the stored pressure in
accumulators reaches the cut-in pressure. The cut-in pressure is not adjustable and is actually controlled by the
adjustment of the cut-out pressure. The accumulator charging spool (23b) will then recycle to bring the stored
pressure in the accumulators back up to the cut-out pressure.

Once the accumulators (25) & (32) are charged equally, the accumulator isolation check valve (23e) separates
the pressurized oil stored is either accumulator. Only one check valve of the accumulator isolation check valve
(23e) can be seated at one time, the highest pressure side. This will always assure that the lowest accumulator
pressure is ported to the accumulator charging valve. If a failure were to occur in either the front or rear brake
circuits, the check valve in the good circuit would close to continue to provide service braking with at least one
circuit.
The brake accumulators store a volume of fluid under pressure to provide a supply of brake function oil without
having the brake pump operating under pressure at all times. Teed into the hydraulic line between the brake
valve and each accumulator 25) & (32) is a redundant pressure switch (27) & (31) and a pressure test ports (26),
(33).

Pressurized oil from the inlet of the accumulator isolation check valve is available to the park brake solenoid
(23d). This solenoid is normally closed and vents the parking brake release port to tank when it is not energized.
The parking brake (22) is spring applied and requires hydraulic pressure to release it. Any time that the parking
brake solenoid is not activated or the brake accumulator pressure is low, the parking brake automatically actua-
tes. There is a parking brake accumulator (24) teed into the inlet of the parking brake solenoid valve.
There is a brake treadle valve (23c) connected to the brake pedal inside the cab. The treadle valve consists of a
control spool for the front brakes and another control spool for the rear brakes. These spools are interconnected
with a spring so that both the front and rear brakes will see approximately the same pressure as the single pedal
is depressed. Each treadle valve provides a variable pressure to its respective service brake actuator in pro-
portion to the effort applied to the brake pedal. The service brake actuators are spring released and require an
applied pressure to actuate the brakes. A small amount of brake pedal force equals low brake pressure applied to
the actuator and hence light braking action. Heavier brake pedal force will result in greater braking action.
The wheel loader brake lights are actuated by a 4.1bar pressure switch (30) .

SERVIVE BRAKE PRESSURE ADJUSTMENT

1 Remove the tamper resistant cover (1)
2 Install a pressure gauge on points 19 or 20
3 Apply and hold the brake for 10 to 15 seconds 2
4 Turn the adjusting bolt (2) to get :
621E: Front Brake: 90-97 bar (1305-1407 psi)
Rear Brake: 87-94 bar (1260-1363 psi) 1
521E Front Brake: 62-68 bar (899-986 psi)
Rear Brake: 59-65 bar (856-943 psi)

4
521E - 621E 5B - BRAKE / COOLING

BRAKE PEDAL VALVE 19 1 28

23d

20
30

5
4 0.16l
97b 7 .8l
55b

6 8

8b rising
6b
103b falling
DS2
S3 S1
0.3
3d 3
 0.65

BR3

 20 3c
cut in 57b
cut out 193b 3b
3e 3a
BR1

Adjustable T N P
Declutch

29

BR2
33
S2

35 34
8 19 6b
DS1
3
3
4.b 30 .8 l
55b

5
5B - BRAKE / COOLING 521E - 621E

COOLING FAN CIRCUIT

The 521E & 621E have a hydraulically driven cooling system fan. The cooling system module is located between
the cab and the engine. The hydraulic reservoir is the center of the cooling system module that also includes
the radiator, the engine charge air cooler, the hydraulic oil cooler, transmission oil cooler, fuel cooler and the AC
condenser. Air flow enters the cooling system module from both the right and left sides of the machine as well
as the top and exits into the engine compartment. This allows the radiator and coolers to remain debris free for
extended periods of time.

The fan drive system uses oil flow from the brake pump (34) that is not required to maintain the brake accumula-
tors charged to drive the fan motor. In standard form, oil flows directly from the brake valve (23) to the inlet of the
fan drive motor (35). The standard fan drive motor is protected by an external relief valve and a check valve that
allows oil to recirculate as the motor freewheels due to fan inertia when the engine stops. Oil returning from the
fan drive motor can either return to the hydraulic oil cooler and then to the hydraulic filter,

The cooling fan drive system can be equipped with an optional fan reverser valve (39) to reverse the airflow throu-
gh the radiator and coolers to clear debris. A rocker switch in the right console in the cab controls the fan reverser
valve in AUTO or MANUAL mode.

In AUTO mode the fan speed is regulated by a proportionnal solenoid valve (B). Highier the pressure setting of the
proportionnal solenoid, faster the fan goes. The pressure setting of the proportionnal solenoid valve depends on 4
values: engine coolant temperature, air intake temperature, hydraulic oil temperature and transmission oil tempe-
rature.
In AUTO mode too, a fan reversing cycle is automatically initiated every 30 mn (only if the engine revolution is
highier 1600 rpm). The 30mn delay can be change using the Electronic Service Tool

In every case (manual or automatic), the fan reversal is disabled if hydraulic oil temperature is below 10°C. If it
is a manual request, an error message is displayed on the AIC screen, so that operator knows why it does not
operate.

A ON /OFF reversing solenoid (39 Ohms)

B Proportionnal solenoid for fan speed control ( 25 Ohms)

35

39

22

6
521E - 621E 5B - BRAKE / COOLING

VARIABLE SPEED FAN VALVE (39)

This valve is designed for two purposes:

To reverse the rotation of the fan drive motor to purge the debris from the radiators and coolers
To control the fan speed depending on temperature values of engine coolant, air intake, hydraulic oil and
transmision oil.
Reversing system
It is controlled by the ON / OFF solenoid valve (A).
With the fan reverser solenoid valve (A) de-energized, for forward direction, the flow is as follows: the flow direc-
tionnal valves (3) and (4) will remain in neutral because return pressure is at both ends and the spring force will
hold them in neutral position. Flow then goes to M2 port and to the motor. From the motor flow goes to M1 port.
As the flow selector (4) remains in neutral the flow from M1 returns to tank.
For reverse operation, the Fan Reverser solenoid (A) is energized. The flow directionnal valves (3) and (4) are
operated because inlet pressure is at the non spring end and return pressure is on the spring end. So flow is
from IN to M1 port and the motor. As the flow selector (3) is activated the flow from M2 returns to tank.
Variable fan speed
It is controlled by the proportionnal solenoid (B) that receives a variable current from AIC. As the current in the
valve (B) increases, the pressure setting of the proportionnal valve decreases and consequently the fan speed
decreases.
After a reversing request (manual or automatic), if the fan was at maximum forward speed, it will take 2 seconds
to get to zero, and 2 seconds again to reach max reversed speed, so that the variation feels smooth.
Relief pressure :
In normal operation the relief pressure is done by the proportionnal solenoid valve (B). In case of a misfunction-
ning of the proportionnal solenoid valve the cross-over relief valve (5) releives the pressure at the setting value.

M2 M1 M1
M2

5
5

240b
240b
3 4 3 4

OFF ON
B A B A
TANK
IN TANK IN

STANDARD FAN VALVE

A hydraulic motor (35) drives the cooling fan. Oil supply
for the drive motor comes from the gear type brake pump
38 35 23a 23 (34), through the brake valve (23). Oil returning from the
fan drive motor passes through an optional oil cooler (38)
and the hydraulic filter and then to the reservoir.
23b The standard fan drive motor is protected by a relief valve
to prevent over pressure and it is protected also by a
check valve to avoid cavitation as the motor freewheels.
135b

7
5B - BRAKE / COOLING 521E - 621E

VARIABLE SPEED FAN VALVE (39)

B A

21
B A 4
3
M M
5
5
3 4

IN

Fan speed with engine at full throttle 521E 621E

Maximum fan speed at 100% 1325 - 1375 RPM 1200±25 RPM

Fan speed ajustment:

Must be done engine running full RPM

1. Select the screen Fan test
2. Press the «ENTER» key
3. Select the sub menu « Fixed 100%»
4. Press the «ENTER» key
5. Select the menu «Ajust Speed»
6. Use the arrow keys to get a reverse video on the number shown
7. Depress the «ENTER» key to get a flashing counter video
8. Use the «UP» or «DOWN» keys to increase or reduce the number (highier is the number, highier is the
fan speed); «UP» or «DOWN» has to be depressed several times
9. At the correct fan speed (engine at full rpm) depress the «ENTER» key to confirm.
10. Depress the «ESC» key to exit the menu.

NOTE: to come back to the default value select ***** and depress the «ENTER» key.

Flashing
ESC UP
Fixed 100% Ajust Speed

Fan Test Fixed 100% Speed. 763

Speed ESC
Press ESC Reset *****
to quit mode ENT
Actual PWM 33
DOWN
ENTER
621E S/N 1N8HE79014

8
521E - 621E 5B - BRAKE / COOLING

VARIABLE SPEED FAN VALVE (39)

Electrical circuit

IGN POWER

J7 BUSS-ECA

J8 BUSS-ECA
AIC_1 AIC_1 AIC_2 AIC_2 PIN ENG/FAN RVSR
ECA F7 (OPTION)
FAN FAN RVSR FAN RVSR FAN RVSR
PWM SIGNAL MANUAL AUTO 7.5 AMP
HIGH LOW HIGH HIGH
26 23 7 8
52 W-0.8
56 W-0.8

52AU W-0.8
52M W-0.8

19P Or-0.8
0_B7 Bk-0.8 sht8,SPL_BCK_LT_GD2
7 7 SPL_PIN
49_Q S-0.8 sht8,SPL_BCK_LGT2
8 8
c 5 5 19P_C Or-0.8 A
a
4 4 B
10 19P_C Or-0.8 C
b 6 6 D
b 1 1 19P_D Or-0.8 E
c 9 19P_E Or-0.8 F
3 3 52AU W-0.8
a 2 2 52J W-0.8
SFC
FAN CONTROL SWITCH
(OPTION)
86 30
ECB

FAN RVSR
K4
(OPTION)

85 87A 87

52 W-0.8
52A_B W-1.0

56_A W-1.0 A A FAN

B B PWM
0_BQ Bk-1.0
SOLENOID
YFN XXX at 20°C
` 1 1 FAN
2 2 REVERSING
0_BB Bk-1.0
SOLENOID
SPL_FAN YFR 39.3 at 20°C

a: variable speed (w/o auto reversing)

b : automatic (variable and auto reversing)
c : manual reversing

9
5B - BRAKE / COOLING 521E - 621E

HYDRAULIC COOLER THERMAL BY-PASS VALVE (37)

521E & 621E can be equipped as an option with a thermal by-pass valve (41) to protect the hydraulic cooler from
pressure spike in cold weather startup and operation. The valve is designed so that oil flows through the cooler
when the oil temperature reaches 49°C .

Cooler. Tank.

IN
M2

34b

M1 T

37
Opening temp : 44° - 53°
Fully opened : 63°

TANK 0.3 to 0.6b

37

10
521E - 621E 5B - BRAKE / COOLING

PARKING BRAKE (22)

Adjustment When the parking brake is released, the gap between the disc and the brake shoes must
be between 0.5mm and 1.5 mm.

Parking brake test Refer section 4

Towing the machine Never tow the machine from the front. Use the rear draw bar hole of the counter weight. If
the machine is to be towed more than 0.8 km disconnect the front and rear drive shaft to
avoid any lubrication problem into the 4WG transmission.

10

11
5B - BRAKE / COOLING 521E - 621E

SERVICE BRAKE

Self adjustment and disc wear check

Measure once a year or before in severe usage

If «X» is lower than 4 mm when the brake is applied replace the lined disc both side.

1 Automatic wear adjustment puller

2 Plug for wear measurement

12
521E - 621E 5B - BRAKE / COOLING

SERVICE BRAKE

To be replaced by the latest version

4 3
13
7
12 8
15 13 11
14

5
6
9

17

16

3 Snap ring
4 Roller pin 5 6
5 Snap ring
6 Puller plate
7 Elastic washer (cuper ring)
8 Self adjustment puller 7
9 Snap ring
10 Brake piston Y
11 Carrier ring 9
12 Back seal
13 U oil seal 8
14 U oil seal
15 Back seal
16 Brake disk; inner
17 Brake plate ; outer

Service
The measurement «Y» must be within 10.5 mm + / - 0.3 mm before disc reassembly.

13
5B - BRAKE / COOLING 521E - 621E

14