S Class air suspension problems

[alc]

Please someone help as they have had it on the computer and it is not showing any faults!!!!!!!!!
First problem was a noisy air suspension (AS) pump so we fitted a used pump. A lot quieter but after about three weeks I had 3 passengers in the rear and it bottomed out. With no rear passengers or luggage it is ok but when you hit a subsised
length of road on the motorway you can hear the rear tyres hit the wheel arch. It also looks slightly lower on the ROS than the RNS. It is not like this all the time though. I took my son and two friends and all their luggage to the airport and had no problems. I think I may have initially raised the suspension and when we were loaded I lowered it with no problems. But today I tried to raise it and nothing happened. Someone has mentioned it may be the valves. The car is a 2001 430 and has only done 70k with a full history. It has not been abused. I know S classes have suspension problems but I cannot understand why their computer is not picking up a fault when there obviously is a fault. PLEASE HELP.

[Aeroresh]

The fact that the computer isnt picking up a fault would lead me in the direction of the height sensors. They are known to seize and stick which then gives false height readings to the computer. Best way to test is disconnect the lower sensor arm off the suspension arm and check that everything moves ok without resistance.

[alc]

Thank you Aeroresh, my mechanic said your advise worked. Will now test it and let you know if it is ok now. Thanks again.

[BoyBlue]

I had a similar problem a couple of years ago, noisy air pump, fitted a new pump, (there is an updated pump now for S Class)frightening when the front wings start rubbing on the tyres.