WM 430149 Troubleshooting The Levelling System: Troubleshooting

Component arrangement - air suspension → 4300IN COMPONENT ARRANGEMENT  - air suspension

1. Troubleshooting air-spring dampers and the levelling system

   Symptom	Fault detection	Possible causes	Solution
   Gradual loss of pressure Vehicle lies to one side after a long time	Observe vehicle height over a long period of time and try to find leak using a commercially available leak detection spray	Leak in air-spring damper	Repair air-spring damper → 433037 DISASSEMBLING AND ASSEMBLING FRONT SPRING STRUT  → 432537 DISASSEMBLING AND ASSEMBLING REAR SPRING STRUT
   		Leak in air lines	Repair air line → WM 438541 REPAIRING PRESSURE HOSE
   		Leak at residual pressure retaining valve	Replace air spring → 433037 DISASSEMBLING AND ASSEMBLING FRONT SPRING STRUT  → 432537 DISASSEMBLING AND ASSEMBLING REAR SPRING STRUT

   Symptom	Fault detection	Possible causes	Solution
   Vehicle lying to one side No leaks in the system	Carry out guided fault finding using the PIWIS Tester	Vehicle level sensor defective	Replace vehicle level sensor → WM 431855 REPLACING FRONT LEVEL SENSOR  Replacing rear level sensor → WM 431955 REPLACING REAR LEVEL SENSOR
   		Linkage or holder for vehicle level sensor is bent

   Symptom	Fault detection	Possible causes	Solution
   Vehicle is too high Vehicle cannot be lowered	1.) Check that the vehicle has sufficient ground clearance	Vehicle position is raised	Look for signs of damage and check clearance around the air-spring dampers and anti-roll bars
   	2.) Examine air line and line routing	Air line blocked, kinked or frozen	Repair kinked air lines; carefully blow out frozen and blocked air lines using compressed air → WM 439155 REPLACING PRESSURE LINE (PDCC)
   	3.) Carry out guided fault finding using the PIWIS Tester	Drain valve in compressor or control valves in valve block do not work	Replace compressor → WM 431519 REMOVING AND INSTALLING COMPRESSOR FOR THE LEVEL CONTROL SYSTEM  Replace valve block → WM 431519 REMOVING AND INSTALLING COMPRESSOR FOR THE LEVEL CONTROL SYSTEM
   	4.) If no faults were found after carrying out Steps 1 to 3, the residual pressure retaining valve no longer allows air to come out (valve jammed)	Residual pressure retaining valve jammed (does not allow any more air to come out)	Replace residual pressure retaining valve → WM 433655 REPLACING RESIDUAL PRESSURE RETAINING VALVE (RDHV)

   Symptom	Fault detection	Possible causes	Solution
   Vehicle is too low Vehicle cannot be raised or can only be raised very slowly	5.) Carry out guided fault finding using the PIWIS Tester	Check relays, plug contacts, wire harness and fuses in the vehicle electrical system
   	6.) Look for leaks at the pressure accumulator using commercially available leak detection spray	Air line or connections to the pressure accumulator defective/leaking	Repair air line → WM 438541 REPAIRING PRESSURE HOSE
   	7.) Carry out guided fault finding using the PIWIS Tester	Drain valve in the compressor defective/leaking/open	Replace compressor → WM 431519 REMOVING AND INSTALLING COMPRESSOR FOR THE LEVEL CONTROL SYSTEM
   	8.) Look for leaks at the compressor using commercially available leak detection spray	Compressor is leaking	Replace compressor → WM 431519 REMOVING AND INSTALLING COMPRESSOR FOR THE LEVEL CONTROL SYSTEM
   	9.) If no faults were found after carrying out Steps 5 to 8, the compressor is faulty	Compressor faulty	Replace compressor → WM 431519 REMOVING AND INSTALLING COMPRESSOR FOR THE LEVEL CONTROL SYSTEM

   Symptom	Fault detection	Possible causes	Solution
   Rapid loss of pressure	Vehicle lying to the left or right; when you try to switch to a different level, you can hear air coming from the defective air spring	Air spring is defective	Repair air-spring damper → 433037 DISASSEMBLING AND ASSEMBLING FRONT SPRING STRUT  → 432537 DISASSEMBLING AND ASSEMBLING REAR SPRING STRUT
   		Air line torn off	Repair air line → WM 438541 REPAIRING PRESSURE HOSE

   Symptom	Fault detection	Possible causes	Solution
   Insufficient damping	Test drive: Adjust the damping level while the vehicle is in motion. You should feel a significant change in the damping effect when driving on uneven road surfaces. Also listen for "rumbling noises"	Damping adjustment valve faulty	Repair air-spring damper → 433037 DISASSEMBLING AND ASSEMBLING FRONT SPRING STRUT  → 432537 DISASSEMBLING AND ASSEMBLING REAR SPRING STRUT
   		Vibration damper worn	Repair air-spring damper; clean air line system → 433037 DISASSEMBLING AND ASSEMBLING FRONT SPRING STRUT  → Air-Spring Strut

2. Perform the following check under these conditions:
   • The vehicle must be standing on a level surface.
   • The vehicle must be cold and must not be moved during the check.
   • The room temperature should be between 10°C and 30°C and must not fluctuate to any great extent.
     • Start the engine.
     • Switch the vehicle to off-road level using the rocker switch (selector switch) for the levelling system (observe display in the instrument cluster). Then lower the vehicle to normal level again.
     • Switch off the engine, ignition off.
     • Pull off connector on the leveling system control unit to prevent a levelling system readjustment. → WM 431619 REMOVING AND INSTALLING LEVEL CONTROL MODULE 
       • Measure the vehicle height -dimension X-  at all four wheels on the vehicle.

         Vehicle height at front axle-dimension X- (from wing to centre of wheel) → Fig 1

         Fig 1: Identifying Vehicle Height At Front Axle - Dimension X- (From Wing To Centre Of Wheel)

         Courtesy of PORSCHE CARS NORTH AMERICA, INC.
       • Measure the vehicle height -dimension X-  Vehicle height at front axle - dimension X- (from wing to centre of wheel) → see Fig 2 again after two hours and compare it with the first measurement.
         Fig 2: Identifying Vehicle Height At Rear Axle - Dimension X- (From Wing To Centre Of Wheel)

         Courtesy of PORSCHE CARS NORTH AMERICA, INC.

   If the vehicle is lying at an angle, there is a leak at the wheel suspension with the greatest difference between the first and second measurement.

   Use commercially available leak detection spray to check the affected air-spring damper, the relevant air line and the residual pressure retaining valve one after the other.

   If there is no difference after two hours, the vehicle height must be measured again after 24 hours. The difference must not be more than 4 mm after 24 hours.

   The following components must also be checked:

   • Air line connections
   • Residual pressure retaining valve
   • Air-spring damper

   If the vibration dampers are defective, oil from the vibration damper may have entered the air supply system. To ensure that the air spring system works perfectly, it is absolutely essential that you clean the system after a fault is found and replace other components.

3. Procedure for repairing the air spring system after a fault is found on the vibration dampers:
   • Screw off the affected line on the air-spring damper and solenoid valve block.
   • Blow out the line several times until it is clean using compressed air by introducing the compressed air at the end of the line at the solenoid valve block.
   • Check for traces of vibration damper oil in the solenoid valve block.

     If vibration damper oil has contaminated the solenoid valve block, it must be replaced.

   • Check the internal line from the compressor to the solenoid valve block.

If there is oil in the internal line, the compressor must be replaced.