HYDRAULIC SYSTEM

S3.50-5.50XM (S70-120XM) [E004, F004];

H3.50-5.50XM (H70-120XM) [K005, L005]

PART NO. 1466217

1900 SRM 743

SAFETY PRECAUTIONS

MAINTENANCE AND REPAIR

• When lifting parts or assemblies, make sure all slings, chains, or cables are correctly

fastened, and that the load being lifted is balanced. Make sure the crane, cables, and
chains have the capacity to support the weight of the load.

• Do not lift heavy parts by hand, use a lifting mechanism.

• Wear safety glasses.

• DISCONNECT THE BATTERY CONNECTOR before doing any maintenance or repair

on electric lift trucks. Disconnect the battery ground cable on internal combustion lift
trucks.

• Always use correct blocks to prevent the unit from rolling or falling. See HOW TO PUT

THE LIFT TRUCK ON BLOCKS in the Operating Manual or the Periodic Mainte-
nance section.

• Keep the unit clean and the working area clean and orderly.

• Use the correct tools for the job.

• Keep the tools clean and in good condition.

• Always use HYSTER APPROVED parts when making repairs. Replacement parts

must meet or exceed the specifications of the original equipment manufacturer.

• Make sure all nuts, bolts, snap rings, and other fastening devices are removed before

using force to remove parts.

• Always fasten a DO NOT OPERATE tag to the controls of the unit when making repairs,

or if the unit needs repairs.

• Be sure to follow the WARNING and CAUTION notes in the instructions.

• Gasoline, Liquid Petroleum Gas (LPG), Compressed Natural Gas (CNG), and Diesel fuel

are flammable. Be sure to follow the necessary safety precautions when handling these
fuels and when working on these fuel systems.

• Batteries generate flammable gas when they are being charged. Keep fire and sparks

away from the area. Make sure the area is well ventilated.

NOTE: The following symbols and words indicate safety information in this
manual:

WARNING

Indicates a condition that can cause immediate death or injury!

CAUTION

Indicates a condition that can cause property damage!

Hydraulic System

Table of Contents

TABLE OF CONTENTS

General ...............................................................................................................................................................

Description .........................................................................................................................................................

Operation............................................................................................................................................................

Hydraulic Pump H3.50-5.50XM (H70-120XM) ............................................................................................

Hydraulic Pump S3.50-5.50XM (S70-120XM) .............................................................................................

Main Control Valve........................................................................................................................................

Steering Control Unit ....................................................................................................................................

Specifications......................................................................................................................................................

Hydraulic System Capacity (Powershift) .....................................................................................................

Hydraulic System Capacity (Hydrostatic)....................................................................................................

Hydraulic Tank Capacity (Powershift and Hydrostatic) .............................................................................

Hydraulic Tank Capacity ..............................................................................................................................

Relief Pressures @ 2200 RPM, 50 to 80 C (120 to 180 F) ............................................................................

Hydraulic Pump Flow to Valve .....................................................................................................................

Steering Priority Flow ...................................................................................................................................

Troubleshooting..................................................................................................................................................

This section is for the following models:

S3.50-5.50XM (S70-120XM) [E004, F004];

H3.50-5.50XM (H70-120XM) [K005, L005]

"THE

QUALITY

KEEPERS"

HYSTER

APPROVED

PARTS

1900 SRM 743

Description

General

This section has the description and operation of the hydraulic system and a brief description of the components
of the hydraulic system. A troubleshooting guide for the hydraulic system is also included.

Description

The hydraulic system includes the circuits for the
mast and steering systems. See Figure 1 and Fig-
ure 2.

The hydraulic pump’s oil flow increases when a hy-
draulic function is activated.

The hydraulic pump receives oil from the hydraulic
tank through a screen in the tank and sends it

through the control valve to the lift, tilt, and steer-
ing systems.

The main control valve controls the flow of hydraulic
oil to the lift, tilt, steering, and auxiliary hydraulic
cylinders. A relief valve in the control valve controls
the lift pressure within the design limits of the hy-
draulic system. The secondary relief valve controls
the hydraulic pressure in the tilt and auxiliary sys-
tems.

HYDRAULIC TANK

HYDRAULIC FILTER

HYDRAULIC GEAR PUMP

STEERING CYLINDER

STEERING CONTROL UNIT

MAIN CONTROL VALVE

MAIN LIFT CYLINDERS

LOWERING CONTROL VALVE

TILT CYLINDERS

10. MAIN OIL SUPPLY
11. STEERING SUPPLY CHECK PORT

Figure 1. Hydraulic System Diagram

Description

1900 SRM 743

The steering control unit is operated by movement of
the steering wheel. The steering control unit controls
the movement of the steering cylinder. The steer-
ing relief valve controls the hydraulic pressure in the
steering circuit.

The hydraulic oil returns from the control valve and
flows through a filter in the hydraulic tank. The filter
removes small particles from the hydraulic oil.

LIFT CYLINDERS

MAIN CONTROL VALVE

HYDRAULIC PUMP

STEERING CONTROL UNIT

STEERING CYLINDER

TILT CYLINDERS

STEERING RELIEF VALVE

LIFT RELIEF VALVE

TILT/AUX RELIEF VALVE

Figure 2. Hydraulic System Schematic

1900 SRM 743

Operation

HYDRAULIC PUMP H3.50-5.50XM
(H70-120XM)

The hydraulic pump has several sections with a sin-
gle set (single stage) of gears. See Figure 3. The
pump has two covers and the gear housing with the
gears. Seals are used to prevent leaks between the
sections. The inlet and outlet ports are on the input
shaft end cover. The input shaft is splined to a fan
pulley. The fan pulley is connected to a drive shaft
that is driven by the engine crankshaft.

INLET PORT

INPUT SHAFT END
COVER

GEAR HOUSING

PORT END COVER

OUTLET PORT

INPUT GEAR
SHAFT

Figure 3. Hydraulic Pump H3.50-5.50XM

(H70-120XM)

The hydraulic pump gets its oil supply from the hy-
draulic tank. Oil from the outlet port goes to the
main control valve. Refer to the Specifications chart
for the rate of flow to the main control valve.

HYDRAULIC PUMP S3.50-5.50XM
(S70-120XM)

The hydraulic pump has several sections with a
single set (single stage) of gears. See Figure 4. The
pump has two covers and the gear housing with the
gears. Seals are used to prevent leaks between the
sections. The inlet port is located on the side of the

pump and the outlet port is located on the back cover.
The input shaft is splined to the hydraulic pump
drive located on the flywheel end of the engine.

INLET PORT

OUTLET PORT

INPUT SHAFT END COVER

GEAR HOUSING

INPUT GEAR SHAFT

OUTLET PORT COVER

Figure 4. Hydraulic Pump S3.50-5.50XM

(S70-120XM)

MAIN CONTROL VALVE

The main control valve controls the lift, tilt, and
attachment functions of the mast and on a pri-
ority basis, provides steering flow to the steer-
ing control unit.

See Figure 5 and Figure 6.

The control valve receives oil from the hydraulic
pump. The main relief valve (lift circuit) is set at
21.4 MPa (3100 psi) H3.50-5.50XM (H70-120XM)
and 22.4 MPa (3250 psi) S3.50-5.50XM (S70-120XM).
The secondary relief valve (tilt and auxiliary circuits)
is set at 15.5 MPa (2250 psi). The drain circuit from
the main control valve is connected to the hydraulic
tank and flows through an internal filter.

Specifications

1900 SRM 743

Figure 5. Main Control Valve H3.50-5.50XM

(H70-120XM)

Oil flow in the main control valve goes first through a
steering flow divider which ensures a priority flow to
steering. Refer to the Specifications chart for the rate
of flow to steering. The excess oil flow over that re-
quired by steering then goes to the main relief valve
and the lift/lower spool. If none of the spools are actu-
ated, the oil flows past all of the spools and returns
to the hydraulic tank. When the lift/lower spool is
actuated to lift, all of the oil flows to the cylinders.
At this time the main relief valve controls the max-
imum pressure in the hydraulic system. If the tilt
spool is actuated, oil can still flow to the auxiliary
spools. When the tilt or auxiliary spools are actuated,
the tilt/auxiliary relief valve controls the maximum
pressure in the hydraulic system.

Figure 6. Main Control Valve S3.50-5.50XM

(S70-120XM)

STEERING CONTROL UNIT

The steering control unit is a rotary valve operated
by the steering wheel that controls the movement of
the steering cylinder. The steering control unit re-
ceives oil from the main control valve by means of
a flow divider that ensures a priority flow to steer-
ing. A relief valve in the main control valve is set at
10.7 MPa (1500 psi) and controls steering inlet pres-
sure. The control unit has a minimum restriction to
oil flow when the steering wheel is not moved. The
control unit has four ports (inlet, return, left, and
right). Two of the ports (left and right) are connected
to the steering cylinder. During the steering opera-
tion, the steering control unit controls the direction of
flow and the amount of oil that flows to the steering
cylinder. The hydraulic oil returns from the steer-
ing cylinder through the steering control to the main
control valve, and then returns to the hydraulic tank
through the filter.

Specifications

HYDRAULIC SYSTEM CAPACITY
(POWERSHIFT)

H3.50XM-4.00XMS (H70-90XM)

53 liter (14 gal)

H4.00XM-5.50XM (H100-120XM)

75 liter (19.8 gal)

S3.50XM-S5.50XM (S70-120XM)

39 liter (10.3 gal)

HYDRAULIC SYSTEM CAPACITY
(HYDROSTATIC)

H3.50XM-4.00XMS (H70-90XM)

78 liter (20.6 gal)

H4.00XM-5.50XM (H100-120XM)

100 liter (26.4 gal)

1900 SRM 743

Troubleshooting

HYDRAULIC TANK CAPACITY
(POWERSHIFT AND HYDROSTATIC)

H3.50XM-4.00XMS (H70-90XM)

45 liter (11.8 gal)

H4.00XM-5.50XM (H100-120XM)

67 liter (17.7 gal)

HYDRAULIC TANK CAPACITY

S3.50XM-5.50XM (S70-120XM)

35 liter (9.2 gal)

RELIEF PRESSURES @ 2200 RPM, 50 to
80 C (120 to 180 F)

Lift circuit H3.50-5.50XM (H70-120XM)

21.4 MPa (3100 psi)

Lift circuit S3.50-5.50XM (S70-120XM)

22.4 MPa (3250 psi)

Tilt and auxiliary circuit

15.5 MPa (2250 psi)

Steering circuit

10.7 MPa (1550 psi)

HYDRAULIC PUMP FLOW TO VALVE

H3.50XM-4.00XMS (H70-90XM) @ 2200
rpm, 50 C (120 F)

116 liter/min (30.6 gal/min) No load
112 liter/min (29.6 gal/min) Rated load

H4.00XM-5.50XM (H100-120XM) @ 2200
rpm, 50 C (120 F)

125 liter/min (33 gal/min) No load
121 liter/min (32 gal/min) Rated load

S3.50XM-5.50XM (S70-120XM) @ 2550 rpm,
80 to 100 C (176 to 212 F)

89 liter/min (23.5 gal/min)

STEERING PRIORITY FLOW

17 to 19 liter/min (4.5 to 5.0 gal/min) @ 9.6 MPa
(1400 psi) & 800 engine rpm

Troubleshooting

PROBLEM

POSSIBLE CAUSE

PROCEDURE OR ACTION

Hydraulic functions will not
operate.

There is no oil or not enough oil in
the hydraulic tank.

Fill tank to correct level.

The hydraulic pump is worn or dam-
aged.

Repair or replace hydraulic pump.

Hydraulic pump drive arrangement
is damaged.

Repair pump drive.

Hydraulic pressure is above
or below specifications.

Relief valve(s) in the main control
valve is damaged or not adjusted
correctly.

Replace relief valve(s).

Hydraulic pump is worn or damaged.

Repair or replace hydraulic pump.

The priority valve or flow divider in
the hydraulic pump does not operate
correctly.

Repair priority valve.

Troubleshooting

1900 SRM 743

PROBLEM

POSSIBLE CAUSE

PROCEDURE OR ACTION

LIFT, LOWER AND TILT CIRCUIT

Slow or no movement of
cylinders.

Relief valve(s) in main control valve
is damaged or is not adjusted cor-
rectly.

Replace relief valve(s).

Large leaks between the spool and
bore in the main control valve.

Replace control valve section.

Control valve spool not fully ex-
tended or retracted.

Adjust control valve linkage.

The hydraulic pump is worn or dam-
aged.

Repair or replace hydraulic pump.

The hydraulic pump drive arrange-
ment is damaged.

Repair pump drive.

Air is in the hydraulic system.

Remove air from hydraulic system.

There is a restriction in the hy-
draulic line(s).

Repair or replace hydraulic line(s).

The load is greater than the capacity
of the system.

Handle only the correct load.

The cylinder seals have leaks.

Repair cylinder.

Lift cylinders retract when
the lift spool is in the neutral
position.

Cylinder seals leak or check valve for
lift spool leaks.

Repair lift cylinder or main control
valve.

Large leaks between the spool and
bore in the main control valve.

Repair main control valve.

Hydraulic line(s) leak.

Repair or replace hydraulic line(s).

Lift cylinder rods momentar-
ily move down when the lift
spool is moved to the lift po-
sition.

The load check valve is damaged.

Repair load check valve.

1900 SRM 743

Troubleshooting

PROBLEM

POSSIBLE CAUSE

PROCEDURE OR ACTION

Tilt cylinder rods move for-
ward when the spool is in
neutral position.

Tilt control spool inside the tilt spool
does not work correctly.

Repair tilt spool section of main con-
trol valve.

Oil leaks between the spool and the
bore.

Repair main control valve.

Hydraulic line(s) leak.

Repair or replace hydraulic line(s).

Tilt cylinder seals have leaks.

Repair tilt cylinder.

STEERING CIRCUIT

The lift truck steers slowly.
The steering wheel is hard
to turn.

The oil level is low. There is no oil in
the tank.

Fill tank to correct level.

The line(s) to the steering control
unit or steering cylinder are dam-
aged.

Replace damaged hydraulic line(s).

Steering relief pressure is below
specifications.

Replace relief valve.

The priority flow divider valve does
not operate correctly.

Repair priority valve.

The hydraulic pump is worn or dam-
aged.

Repair or replace hydraulic pump.

The steering wheel turns the
tires in the wrong direction.

The steering control unit is worn or
damaged.

Repair or replace steering control
unit.

The steering supply lines are re-
versed.

Reverse supply lines.

NOTES

____________________________________________________________

TECHNICAL PUBLICATIONS

1900 SRM 743

6/05 (10/03)(11/01)(8/99) Printed in United Kingdom

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