M0123405-00

September 2020
1 4

17 15 2

18
SOS 7 6

(Dimensions: 48 inches x 35 inches)

Component Locations
Schematic Machine
DD Description
Location Location

M0123405-00
Accumulator Gp - Hydraulic (Uncharged) I-9 1
Cylinder Gp - Boom J-9 2
Cylinder Gp - Bucket J-8 3
Cylinder Gp - Stick J-12 4
Filter Gp - Case Drain A-7 5
3 Filter Gp - Hydraulic Return A-8 6
Filter Gp - Oil (Hydraulic) J-4 7
Motor Gp - Swing C-8 8
Motor Gp - Travel (LH)
Motor Gp - Travel (RH)
D-14
D-12
9
10 320 GX and 323 GX Excavator
Hydraulic System
Pump Gp - Main Hydraulics C-4 11
Sensor Gp - Pressure (Boom Cylinder Head End) J-8 12
Sensor Gp - Pressure (Pump 1) D-6 13
Sensor Gp - Pressure (Pump 2) D-7 14
GWX1-UP
Sensor Gp - Pressure (Stick Cylinder Head End) I-6 15
Swivel Gp A-12 16
KTB1-UP
Valve Gp - Check (Return) I-12 17
Valve Gp - Main Control H-4 18

14
13

36 Page,
11

9 Tap Locations
Pressure, Sampling, and Sensor
Tap Schematic
Description
Number Location
AA Pump 1 Pressure Port C-6
BB Pump 2 Pressure Port C-3
CC Case Drain Pressure Port A-4
FRONT REAR 5 DD
SOS
Pilot Pressure Port
Oil Sampling Pressure Port
E-11
H-10

10

MAIN CONTROL VALVE MACHINE RIGHT SIDE VIEW

FLUID POWER SYMBOLS

BB AA
12 16 BASIC COMPONENT SYMBOLS

MAIN AUX

PUMP OR MOTOR FLUID CONDITIONER SPRING CONTROL VALVES RESTRICTION LINE RESTRICTION PUMP PUMP
(FIXED) (2 - SECTION) (VARIABLE & PRESSURE
COMPENSATED)

VARIABILITY SPRING LINE RESTRICTION PRESSURE HYDRAULIC PNEUMATIC LINE RESTRICTION ATTACHMENT
(ADJUSTABLE) (VARIABLE) COMPENSATION ENERGY TRIANGLES (VARIABLE & PRESSURE
COMPENSATED)

VALVE ENVELOPES VALVES VALVE PORTS

ONE POSITION TWO POSITION THREE POSITION TWO - WAY THREE - WAY FOUR - WAY

CONTROL VALVES CHECK VALVES

AB A B

P T P T
BASIC SPRING SHUTTLE PILOT
NORMAL POSITION SHIFTED POSITION INFINITE POSITION
SYMBOL LOADED CONTROLLED

FLUID STORAGE RESERVOIRS

VENTED PRESSURIZED RETURN ABOVE FLUID LEVEL RETURN BELOW FLUID LEVEL

MEASUREMENT ROTATING SHAFTS

PRESSURE TEMPERATURE FLOW UNIDIRECTIONAL BIDIRECTIONAL

COMBINATION CONTROLS

CC SOLENOID SOLENOID
OR MANUAL
SOLENOID
& PILOT
SOLENOID &
PILOT OR MANUAL
SERVO THERMAL DETENT

MANUAL CONTROL SYMBOLS

PUSH - PULL LEVER MANUAL SHUTOFF GENERAL MANUAL PUSH BUTTON PEDAL SPRING

RELEASED PRESSURE PILOT CONTROL SYMBOLS REMOTE SUPPLY PRESSURE

EXTERNAL RETURN INTERNAL RETURN SIMPLIFIED COMPLETE INTERNAL

SUPPLY PRESSURE

ACCUMULATORS CROSSING & JOINING LINES HYDRAULIC & PNEUMATIC CYLINDERS

SPRING LOADED GAS CHARGED LINES CROSSING LINES JOINING SINGLE ACTING DOUBLE ACTING

HYDRAULIC PUMPS HYDRAULIC MOTORS INTERNAL PASSAGEWAYS

FIXED VARIABLE DISPLACEMENT FIXED VARIABLE DISPLACEMENT INFINITE

DISPLACEMENT NON-COMPENSATED DISPLACEMENT NON-COMPENSATED POSITIONING 3 POSITION 2 POSITION

UNIDIRECTIONAL UNIDIRECTIONAL

8
FLOW IN ONE PARALLEL CROSS FLOW IN
BIDIRECTIONAL BIDIRECTIONAL DIRECTION FLOW FLOW EITHER
DIRECTION

© 2020 Caterpillar. All Rights Reserved. CAT, CATERPILLAR, LET’S DO THE WORK, their respective logos, “Caterpillar Yellow,” the “Power Edge”
and Cat “Modern Hex” trade dress, as well as corporate and product identity used herein, are trademarks of Caterpillar and may not be used without

MACHINE TOP VIEW PUMP VIEW permission.

ELECTRICAL SYMBOLS TABLE

HYDRAULIC SYMBOLS (ELECTRICAL)

G
M
TRANSDUCER TRANSDUCER GENERATOR ELECTRIC MOTOR
(FLUID) (GAS / AIR)

PRESSURE SWITCH PRESSURE SWITCH TEMPERATURE ELECTRICAL WIRE

(ADJUSTABLE) SWITCH

WIRE NUMBER IDENTIFICATION CODES

ELECTRICAL SCHEMATIC EXAMPLE HYDRAULIC SCHEMATIC EXAMPLE

CURRENT STANDARD CURRENT STANDARD

HARNESS IDENTIFICATION CODE THIS EXAMPLE

INDICATES WIRE 135 IN HARNESS “AG”
WIRE WIRE
COLOR
CIRCUIT NUMBER
325-AG135 PK-14 IDENTIFICATION WIRE COLOR

CIRCUIT NUMBER WIRE GAUGE*

*Wire gauge is shown in AWG (American Wire Gauge)
IDENTIFICATION but could also be shown in metric denoted with mm 325-PK

PREVIOUS STANDARD

WIRE WIRE COLOR

325-PK-14 B A

CIRCUIT NUMBER WIRE GAUGE* (EXAMPLE VALVE)

IDENTIFICATION *Wire gauge is shown in AWG (American Wire Gauge)
but could also be shown in metric denoted with mm
 14 13 12 11 10 9 8 7 6 5 4 3 2 1
ATTACHMENT VALVE #1 EXTEND
31
PRESSURE SOLENOID
(4) STICK CYLINDER (2) BOOM CYLINDER (7) FILTER GP - OIL 25 HEAVY LIFT SOLENOID

490-4144 510-9212 (3) BUCKET CYLINDER (HYDRAULIC) 24 STRAIGHT TRAVEL SOLENOID

490-4180 SINGLE SINGLE 23 RIGHT TRAVEL BACKWARD SOLENOID
224-1687
22 RIGHT TRAVEL FORWARD SOLENOID
FOR USE AS W/ HAMMER RETURN FILTER
J 21 LEFT TRAVEL BACKWARD SOLENOID J
20 LEFT TRAVEL FORWARD SOLENOID
BR2 19 SWING RIGHT SOLENOID
(Dimensions: 48 inches x 35 inches)

(12) SENSOR GP - PRESSURE 18 SWING LEFT SOLENOID

17 BUCKET CYLINDER RETRACT SOLENOID
(BOOM CYLINDER HEAD END)
338-6971 AUX 16 BUCKET CYLINDER EXTEND SOLENOID
M0123405-00

15 PUMP TO STICK HEAD END SOLENOID

RETURN
14 STICK CYLINDER EXTEND SOLENOID
13 STICK CYLINDER RETRACT SOLENOID
AR5
12 BOOM CYLINDER RETRACT SOLENOID
11 PUMP TO BOOM HEAD END SOLENOID
AL3 BL3 BR3 AR3 AR2 10 BOOM CYLINDER EXTEND SOLENOID
(17) VALVE GP 9 HYDRAULIC LOCK SOLENOID
CHECK (RETURN) 8 SWING PRIORITY SOLENOID
I I
490-3958 7 SWING BRAKE SOLENOID
6 TRAVEL SPEED SOLENOID
AUX 2 SPEED SWG 5 STICK UNLOAD SOLENOID
CV-T TRAVEL PRKG BK
RETURN (1) ACCUMULATOR GP 2 MAIN HYDRAULIC PUMP #2 SOLENOID
CONTROL CONTROL (15) SENSOR GP - PRESSURE 1 MAIN HYDRAULIC PUMP #1 SOLENOID
D HYDRAULIC (UNCHARGED)
C 352-6860 (STICK CYLINDER HEAD END) IDENT ELEC DEVICE NAME
338-6971
SOS AL3 AL2 AL1 AR1 AR2 AR3
36 Page,

Pi5 SG Pi4 PAC CV-Dr

B 6 24
7 11 13 18 23 16 12 (18) VALVE GP
21
MAIN CONTROL
H H
598-1887
BPi Dr1
AR5

MU

Dr2 Pi2 A AL3 AL2 AL1 SHS AR1 AR2 AR3 AR5 MU Pi3 Dr3
T <UP> <IN> <OUT> <L> <BKWD> <BKWD> <CLOSE> BKHS <DOWN> <UP> <OUT>

Dr4

BOOM(1)

AUXILIARY(1)
BUCKET
G G

TRAVEL(R)
Pi6

STICK(2)
STR-TRAVEL
TRAVEL(L)
BOOM(2)

STICK(1)

SWING
Dr6

F F
SWG PRI

STK UNL

Dr7
SRS <OUT> <IN> <R> <FWD> P2S P1S <FWD> BR1 <OPEN> BR2 BKRS <UP> <DOWN> BR3 <IN> <EXT>
Pi1 BL3 BL2 BL1 P2 P1

E DD E
31
P2 P1

8 5
9 14 19 17
20 22 10

SPi bST
BR3
BL3
BL2 BL1 bST BR1 BR2

(14) SENSOR GP - PRESSURE (13) SENSOR GP - PRESSURE

D D
(PUMP 2) (PUMP 1)
338-6971 338-6971

(9) MOTOR GP (10) MOTOR GP

TRAVEL (LH) TRAVEL (RH)
582-9758 582-9758 SWG (11) PUMP GP
TRAVEL MOTOR (LEFT) TRAVEL MOTOR (RIGHT) PRKG BK MAIN HYDRAULICS
Dr Dr CONTROL 593-8367
SWING MOTOR P1 P2
AA BB
PG (8) MOTOR GP 1 2
C SWING ADJ1 ADJ2 C
SWG-Dr 320GX : 587-4953
DB MA1 A1 A2 MA2
323GX : 587-4954
Pi Pi
MU LINE PATTERNS
M Pressure Line
P3 P3
Pilot / Load Sensing Pressure
P2 P2 PA PB
Drain / Return Lines

Q MIN
Q MIN
Air Line

DRAIN Component Group

FILTER CALLOUTS
YY Taps (Pressure, Sampling, Sensor - by letter)

B DL DL D Connectors (By letter) B

Callout Number Component
(Machine Location from (52) VALVE GP - CONTROL Name
Component LocationsTable)
138-1234 Part Number

Q MAX

Q MAX
A B d P B A CV-Dr bST
HYDRAULIC CIRCUIT COLOR DESCRIPTIONS
A C PILOT CONTROL CIRCUIT
PUMP 1 OUTPUT

CV-T T1 TRAVEL LEFT CONTROL CIRCUIT

SUPPLY LINE
B D STICK CONTROL CIRCUIT
SWING CONTROL CIRCUIT

AL1 BR1 (5) FILTER GP MC1 S1 T2 MC2 DRAIN / RETURN LINE

SWING BRAKE CIRCUIT
B' D' CASE DRAIN PUMP 2 OUTPUT
A FA Dr FB B 491-6075
TRAVEL SPEED CONTROL CIRUIT
BL1 AR1 BUCKET CONTROL CIRCUIT
TRAVEL RIGHT CONTROL CIRCUIT
A' C' BOOM CONTROL CIRCUIT
AUXILIARY CONTROL CIRCUIT
d' P'
A SWG-Dr
(16) SWIVEL GP
CC A
234-4440
2 SPEED BL2 AL2
DRAIN THIS SCHEMATIC IS FOR THE 320 GX AND 323 GX EXCAVATOR HYDRAULIC SYSTEM
TRAVEL (6) FILTER GP
FILTER Do not operate or work on this product unless you have
MEDIA NUMBER: M0123405-00
CONTROL HYDRAULIC RETURN
read and understood the instruction and warnings in the
relevant Operation and Maintenance Manuals and SCHEMATIC PART NUMBER: 590-3207, CHANGE: 02, VERSION: HE
relevant service literature. Failure to follow the instruc-
Components are shown installed on a fully operable machine with the key and engine off.
591-8630 tions or heed the warnings could result in injury or
death. Proper care is your responsibility. Refer to the appropriate Service Manual for Troubleshooting, Specifications and Systems Operations.
Refer to the Parts Manual using a specific serial number prefix in SIS before ordering parts from this schematic.

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