The hydraulic system:

Main menu hydraulics
The complete hydraulic system

The Brake system
The height control system

The fluid pressure control
The hydraulic diagrams


The height control system:

Diagnostics table
Conjunction of components

   Front height control valve
   Rear height control valve
   Rear height control rams

   Restrictor valve
   Rollrestrictor valve
   Solenoid valve


Diagnostics table of the height control system

This page contains a comprehensive table to determine the causes of failures on the height control system and the actions that can be taken to solve the problems.


Possible cause


Warning light(s) fail to extinguish immediately engine is started.
warning lamp(s) illuminate whilst car is being driven.

1. Lack of fluid in reservoir.

2. Pressure switch(es) failure.
3. Hydraulic pump(s) failure.
4. Hydraulic accumulator(s) failure.
5. Internal leakage in system(s).

1. Check level; visually check systems for external leakages.
2. Test pressure switch(es).
3. Test pump(s).
4. Test accumulator(s).
5. Test system(s) components for correct operation.

Warning lamp(s) illuminate briefly whilst car is being driven slowly and brakes are actuated.

Accumulator diaphragm failure.

Test accumulator(s).

Height control action noisy, emitting squawks when operating.

Air in heigt control system.

Bleed system.

Car fails to level quickly when 'fast' height control is selected (neutral gearchange position (P or N) or door open).

1. Solenoid wiring circuit faulty.
2. Solenoid valve faulty.
3. Solenoid-restrictors blocked.
4. Height control or roll restrictor valves faulty.

5. Insufficient pressure available.

1. Check wiring circuit.
2. Test solenoid valve.
3. Check restrictors.
4. Check valves for correct fast height control operation.
5. Accumulator failing to give full pressure due to dirt in valves. Test accumulator and test hard spot in height control valve movement.

Car fails to attain correct standing height.

1. Height control valve links incorrectly set.
2. Insufficient pressure available.

1. Adjust links.
2. Check system available pressure; test for leakage.

Car fails to level at front resp. rear.

1. Leakage in pipes, valves or rams.

2. Front resp. rear height control valve links incorrectly adjusted.
3. Front resp. rear height control valve faulty.
4. Car overloaded.
5. Roll restrictor valve faulty (only if symptom is in front).

1. Check visually for leakage and test for internal leakage.
2. Adjust valve links.

3. Test valve.
4. Reduce load.
5. Test roll restrictor valve.

Car fails to level at one side at front

1. Hydraulic ram seal failure.
2. Pipe leakage between roll restrictor and ram.

1. Check ram for seal leakage.
2. Visually check for leaks.

Car fails to level at one side at rear.

1. Hydraulic ram seal failure.
2. Pipe leakage between height control valve and ram.
3. Height control valve failed.

1. Check ram for seal leakage.
2. Visually check for leakage.

3. Test height control valve for correct operation.

Car rolls excessively when cornering and steering becomes unpredictable, causing sudden swerves.

1. Roll restrictor valve permanently in 'fast' condition.
2. Solenoid valve on permanent 'fast'.

1. Test roll restrictor for operation.

2. Test solenoid valve.


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