Fault Diagnosis - Page 10, 11

Fault Diagnosis

Analysis of warranty claims data and dealer reports on the power hydraulic system, have identified customer complaints, that are detailed and dealt with in this section. A brief description of the problems, symptoms and possible causes are given, followed by a diagnostic fault trace, designed to assist rapid and accurate diagnosis.

1. Valve Block Groan

Customer Complaint: Rasping noise from the front of the car (around valve body area) soon after the vehicle has stopped. Particularly evident after the car has been driven enthusiastically. May also occur during trim down compensation after the vehicle is parked.
Cause: Rush of fluid through the down solenoid valve.
Recommended action: Fit latest condition down solenoid valve. See 6, Page 8.

2. Pedal "Off-load" Noise

Customer Complaint: Knocking from front of car (around valve body area) on release of the brake pedal, after braking.
Cause: Vibration of mechanical part of the unloader valve, due to flow of fluid.
Recommended action: See 8, Page 9.

3. Strut Knock

Customer Complaint: Knocking/banging from rear of car, more pronounced on uneven surfaces.
Cause: Decay of trap line pressure due to losses through the down solenoid valve and the non-return valve. This allows the mechanical parts of the struts to "knock" together.
Recommended action: See 2 and 6, Page 8. For cases which are due to "trap line pressure decay" as a result of prolonged periods of non operation of the ride level system, fitthe latestride level sensor, check the level of PHB high pressure hose fitted and on vehicles prior to VIN. 594576 replace the pressure relief valve in the valve block, see 10 and 11, Page 9, also refer to tests 6 and 7, Pages 15 and 16.

4. VCM Low Pressure Warnings

Customer Complaint: Low brake pressure warning displayed on the VCM when the engine is idling. Warning can be extinguished by increasing the engine speed.
Cause: Unloader valve seat wear.

Page 9, also refer to tests 4 and 5, Pages 14 and 15.

5. Accumulator Switches Leaking

Customer Complaint: HSMO fluid leakage from the accumulator switch seals. This fluid may run along the switch cables, between the insulation and cable, into the connector block.
Cause: Switch internal seal leakage.
Recommended action: Thoroughly clean switch cables and connector blocks to remove all traces of HSMO fluid. Replace any affected switch with the latest condition switch. See 5, Page 8.

Fig.3:

6. Fluid Reservoir Leaks (90 MY on)

Customer Complaint: HSMO fluid leaks from the reservoir cap seal or stub pipe joints.
Cause: Cap seal and stub pipe leakage.
Recommended action: For stub pipe leakage - Fit latest condition reservoir. Refer to 9, Page 9. Forcap seal leakage - Fit alternative cap seal (available from Parts Division, Part No. CCC 2782). Remove the filler cap from the reservoir and using a suitable implement, remove the seal from behind the retaining flange, "1" Fig.3. Discard the seal. Clean the cap and reservoir neck. Locate the new seal in the cap, seating the seal against the retaining flange, as shown in "2" Fig.3.

DO NOT LOCATE THE NEW SEAL BEHIND THE RETAINING FLANGE.

Check the fluid level and top up as necessary. Replace the filler cap.