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CG938H Wheel Loader. Manual - part 16

IMPORTANT

Dismounting and servicing of vane pump by untrained maintenance staff is strictly
prohibited.

CAUTION

When replacing rubber tube assembly in vane pump, loader engine should be shut off

first to release pressure and cool down hydraulic oil (to a safe degree) before the

replacement is made.

2. Steering gear: Eaton BZZ-800 static (splined connection)

1、a Operating principle: the functionality is realized by a load-sensing system. The flow rate

going through steering gear is quite low when steering gear is in neutral position to keep

constant pressure and save energy for the system. During power steering, pressure oil

enters stator through valve plug and valve bush, and pushes the rotor to rotate with

steering wheel to transfer the oil pressure to the left or right chamber of steering cylinder,

thus realizing steering by pushing guide wheel with cylinder piston rod. Oil in the other

cylinder chamber returns to oil tank through steering gear.

2、b Installation:

3、Make sure that steering gear installed is coaxial to steering post with clearance kept in

axial direction to avoid dieback of valve plug. Check steering wheel to see if opposite

rotation is smooth after installation.

4、c Pipelines should be installed as per the four oil ports marked on steering gear:

5、“P” – to be connected with oil pump;

6、“T” – to be connected with oil tank;

7、“L” and “R” are to be connected with left and right chamber of steering cylinder

respectively.

8、d Structure of steering gear is given in the right view:

9、e Diagram of FK combination valves:

10、 1. Be careful not to bump or scratch the working surface or end surface of various

parts.

11、 2. Do not soak the dismounted rubber ring in gasoline to avoid deformation or

deterioration due to action between rubber and gasoline.

12、 3. Dismounting and servicing of steering gear by untrained maintenance staff is strictly

prohibited.

13、 4. Simultaneous hard steering by two people is strictly prohibited.

14、 CAUTION

When replacing rubber tube assembly in steering gear, loader engine should be shut off

first to release pressure and cool down hydraulic oil (to a safe degree) before the

a Structure and principle

IMPORTANT

Dismounting and servicing of priority steering control valve by untrained maintenance staff is

strictly prohibited.

CAUTION

When replacing rubber tube assembly in priority steering control valve, loader engine should

be shut off first to release pressure and cool down hydraulic oil (to a safe degree) before the

replacement is made.

IMPORTANT

Dismounting and servicing of steering cylinder by untrained maintenance staff is strictly

prohibited.

CAUTION

When replacing rubber tube assembly in steering cylinder, loader engine should be shut off

first to release pressure and cool down hydraulic oil (to a safe degree) before the replacement is

made.

5. Emergency steering:

Steering system features emergency steering function. When a sudden failure occurs to

steering pump, etc., pressure in steering system drops quickly and the emergency steering is

automatically started when the pressure drops to 2 Mpa（20kg）

Emergency steering power unit: model number: 11551-00.

The ascending flow curve allows emergency steering system to have adequate steering power and

velocity. Steering control components is able to turn from neutral position to the position of steering

angle measured in B.3.2 (i.e. 38º/2=19º) in 6 seconds after the operation begins. Forward velocity

should be kept at (10±2) km/h, and steering control force should not exceed 350N.

IV. Pressure relief of system:

Turn off engine and then turn steering wheel leftward and rightward for several times to

eliminate internal pressure of pipeline system.

Hydraulic oil leakage in pipelines may cause accident and leads to personal injury or death.

Leaking pipeline is damaged and should be replaced. When replacing pipeline, first eliminate

(release) pressure and cool down hydraulic oil (to a safe degree) before the replacement is

made.

V. Lubrication of oil cylinder pin:

V. Lubrication of oil cylinder pin:

The lubrication of fore and rear oil cylinder pin assembly: add lubricant with a grease gun according

to the position specified in the figure.

VI. Troubleshooting of hydraulic steering system

Failure Symptoms

Causes

Solutions

Dirt on joint faces

Check and clean joint

faces

Shaft sealer ring damaged

Replace sealer ring

Oil leakage

Leakage on joint faces of

parts

Leakage at front cover

Leakage at screws

Insufficient tightening

torque of screw

Tighten screw

Heavy

steering

Steering is heavy in fast

turning and light in slow

turning

Insufficient oil supply

Check pump and priority

steering control valve

Oil cylinder crawls with

irregular noise and bubbles

in oil

Air in steering system

Eliminate air in steering

system and check pump

inlet for leakage

Heavy steering, and no

steering cylinders do not

work

Manual steering check valve

failure

Check for existence of

steel ball and jam by dirt

Oil cylinders do not work

Leakage at FK overload

valve or in cylinder

Replace FK combination

valve and check cylinder

for internal leakage

Light steering with zero load

and heavy steering with

heavy load

FK safety valve leakage or

safety valve spring failure

Replace FK combination

valve

Heavy steering

High hydraulic oil viscosity

No opposite rotation

Spring leaf failure

Replace spring leaf

Marked increase of pressure

runout, and even steering

failure

Bent or broken key, crack in

universal driving shaft

keyway

Replace key or universal

driving shaft

Steering

malfunction

Opposite rotation or

wagging of steering wheel

immediately after steering

Misplacement of universal

driving shaft and rotor

Reassemble

No manual

steering

Cylinder piston reaches limit

and no sense of steering

dead end in power steering,

steering cylinders do not

work in manual steering

Large radial or axial

clearance in stator and rotor

Replace stator and rotor

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