Usage:
Important Information
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When removing hydraulic pipes ensure that there is no pressure in the lines. Lower the suspension and secure the hand lever in the 'lower' position so that the accumulator and front suspension cylinders are connected to tank through the control valve. |
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Do not work between the wheel and wheel arch. There is not enough clearance in this area to allow a man to work safely. |
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Some of the procedures which follow require the suspension control valve hand lever to be operated without first disconnecting the air lines. BE PREPARED - the lever will tend to "kick back" when air pressure enters the cylinder. |
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Troubleshooting
PROBLEM: Suspension control valve hand lever is hard to move.
POSSIBLE CAUSES:
- 1. Damage to the lever linkage.
- 2. Suspension control valve spool sticking.
PROBLEM: Suspension will not level correctly.
POSSIBLE CAUSES:
- 1. Damaged relief valve cartridge in suspension control valve.
- 2. Suspension control valve spool sticking.
- 3. Filter element clogged.
- 4. Failure of the air supply.
- 5. Rotary valve actuator arm damaged or loose.
- 2. Suspension control valve spool sticking.
PROBLEM: Suspension fails to maintain the correct height.
POSSIBLE CAUSES:
- 1. Leakage across suspension control valve spool.
- 2. Leakage from pipes and fittings.
PROBLEM: Suspension ride too soft/hard.
POSSIBLE CAUSES:
- 1. Accumulator pre-charge pressure too high/low.
- 2. Accumulator piston seals damaged.
Suspension Control Valve
Relief Setting
To check the pressure at which the relief valve opens:
1. Install a pressure gauge at the quick disconnect coupling on the test port. Use the 0-35000 kPa (0-5000 p.s.i.) gauge on CAT test tool 9S7370 with 6V4144 coupling.
Field Test Port - Early Trucks
Field Test Port - Later Trucks
2. Start the engine and operate at low idle.
3. Use the suspension control valve hand lever to fully raise the suspension and hold until the relief valve opens.
4. If the valve setting is incorrect the relief valve cartridge must be replaced. The relief valve is not adjustable.
Accumulator Precharge Pressure
To check and adjust the accumulator precharge pressure use the CAT charging assembly 7S5437.
1. Park the truck on level ground and stop the engine.
2. Use the suspension control valve hand lever to lower the suspension fully. This allows the oil at the bottom of the piston accumulator to return to tank. Secure the lever in the "lower" position.
3. Remove the guard and protective cap from the accumulator gas valve.
Accumulator Gas Valve
Charging Equipment
4. Use the 0-14000 kPa (0-2000 p.s.i.) gauge (3) and ensure that valve (2) is closed.
5. Attach connector (4) to the accumulator gas valve.
6. Turn valve (5) clockwise until it is screwed fully down. The accumulator precharge pressure will be shown on the gauge (3).
7. If the pressure is high remove the quick disconnect coupling (1) and crack valve (2) until the gauge registers the correct value.
8. If the pressure is low attach the quick disconnect coupling (1) to valve (2) and attach regulator (6) to the nitrogen cylinder.
9. With valve (2) closed, open the nitrogen cylinder valve and adjust screw (7) until gauge (8) registers the correct precharge pressure.
10. Open valve (2), allow the accumulator to charge and close valve (2). If the pressure registered on the gauges (3 & 8) is the same, the accumulator is properly charged. Repeat if necessary until the gauge readings agree.
11. Close valve (2) and the nitrogen cylinder valve.
12. Turn valve (5) fully counter-clockwise. Remove the test equipment.
13. Start the engine, release the hand lever and allow the suspension to return to the 'level ride' position.
Charging A Rebuilt Accumulator
It is necessary to remove all the air from the nitrogen end of the accumulator. When the accumulator is rebuilt, put 2 litres (0.50 U.S. gallons) of hydraulic oil in the nitrogen end. This oil is used to vent the air from the accumulator and to lubricate the piston top seal. Install the accumulator on the truck leaving the hydraulic line disconnected and charge as follows:
1. Use the same CAT charging equipment as used to charge the accumulator.
2. Attach connector (4) to the accumulator gas valve. Turn valve (5) clockwise until it is fully screwed down.
3. With valve (2) closed, open the nitrogen cylinder valve and adjust screw (7) until gauge (8) registers approximately 690 kPa (100 p.s.i.).
4. Open valve (2), allow the accumulator to charge and close valve (2). This will move the piston down to the bottom of the accumulator to exhaust air from below the piston. Attach the hydraulic connection to the accumulator.
5. Remove the quick disconnect coupling (1) and crack valve (2) to release the gas pressure above the piston. Start the engine and use the hand lever on the suspension control valve to raise the suspension. The piston in the accumulator will rise and expel any air and surplus oil. The suspension will rise and charge the oil side of the accumulator. Stop the engine.
6. Close valve (2) and attach the quick disconnect coupling (1).
7. Move the hand lever on the suspension control valve to the 'lower' position and secure. Follow steps 9 through 13 of 'Charging the Accumulator'.
8. End by installing the charge valve protective cap and guard. Start the engine and manually raise and lower the suspension a few times to purge any air out of the system. Stop the engine.
Front Suspension
To check and adjust the front suspension:
1. Position the truck on level ground with the brakes off and the inter-axle differential lock disengaged. Stop the engine.
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Chock the rear wheels to make sure the truck remains stationary. |
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2. Make sure the hydraulic system oil is at normal operating temperature and the air system pressure is normal.
3. Carry out a functional check of the rotary valve:
a) Hold arm (1) steady in the horizontal mid position and disconnect the adjusting link upper ball joint (2).
b) Start the engine, operate at low idle and move arm (1) downward through about 30°. After 4 to 7 seconds the truck should start to rise. Return the arm to the mid position and the movement should stop.
c) Move the arm upward through about 30°. After 4 to 7 seconds the truck should start to lower. Return the arm to the mid position and the movement should stop. Stop the engine.
d) Connect the adjusting link upper ball joint (2) to the arm (1). The suspension should return to the 'level ride' position when the engine is started.
4. Check and adjust the suspension height:
a) Allow the suspension to settle at the 'level ride' position.
b) Apply the park brake and shut down the engine.
c) Measure the distance between the wheel arch and tire (dimension X) and note the dimension.
d) Release the park brake, and use the hand lever on the suspension control valve to fully lower the suspension (push down on the lever).
e) Measure the distance between the wheel arch and tire (dimension Y) and note the dimension. Dimension X minus dimension Y should equal 145-175mm if the suspension ride height is correctly set.
f) If the ride height is correct start the engine, allow the suspension to self level, apply the park brake and shut down the engine. If the ride height is wrong continue as follows.
g) Disconnect the ball joint (2) from the arm (1) and wedge the arm in the horizontal mid-position.
h) Start the engine, allow to operate at low idle and release the park brake.
i) Use the hand lever on the suspension control valve to raise the suspension (push up on the lever) until dimension X equals dimension Y plus 160mm.
j) Stop the engine and apply the park brake.
k) With arm (1) still in the horizontal mid-position adjust the ball joint (2) until it can be located without deflecting the arm. Lock the ball joint in position and fix it to the arm.
l) Start the engine, release the park brake and allow the engine to operate at low idle for 20 seconds.
m) Stop the engine, apply the park brake and check that dimension X is still within 15mm of the dimension measured in step (i).
Rotary Valve and Actuator
Suspension Valve Hand Lever
Rear Suspension
The rear suspension will require bleeding and adjusting if any work has been carried out on the system.
1. Start the engine and run at low idle. Allow the suspension to "self level" before proceeding.
2. Open the bleed valves (1) on the pipes connecting the full bore sides of each pair of suspension cylinders.
3. Open both flow control valves (2) located at the hitch end of the rear frame. Allow the oil to bleed out until it flows free of any air bubbles.
NOTE: Catch split oil in a suitable container.
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Wipe oil spillage off the truck to avoid a fire hazard. Wipe split oil off the floor or apply a suitable absorbent material to prevent accidents. |
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4. Close both flow control valves (2) and bleed valves (1).
5. Open the flow control valves and allow the rear suspension to extend fully. Close the control valves.
6. Open the bleed valves and allow the rear suspension to fully lower. Close the bleed valves.
7. Open one flow control valve (left or right hand side) and allow the suspension on the same side of the machine to rise until the total amount of chromed rod visible from the pair of cylinders is equal to Dimension B - see SPECIFICATIONS. Close the flow control valve.
8. Open the opposite hand flow control valve and allow the suspension on that side of the machine to rise until the total amount of chromed rod visible from the pair of cylinders is equal to Dimension B. Close the flow control valve.
9. Stop the engine. Check the hydraulic oil level and top up if necessary. Ensure that the correct make-up oil is used.
Bleed Valve
Flow Control Valve
Rear Suspension Cylinders