W220 S Class air suspension

[SLK230Auto]

Hi,
I have a 2002 W220 320 CDi S Class that has the following annoying trait;
When parked and locked, the air suspension (notably the rear) rises over a period of time, say 8 hrs - this rise is around 3" or so. As soon as i unlock the car, the self levelling electrics activate and the car drops to its normal running level. If left unlocked it will eventually continue to rise then self lower until the air from the reservoir is exhausted. If unlocked and started then the car will remain at the correct level as the air compressor will keep the cylinder topped up.
Now then, am i correct in my diagnosis that it will be the air valve assembly at fault as this is the only component that can let air from the cylinder to the struts once the car is locked.
Any advice before i purchase a new one (air valve that is!) will be appreciated.

 

[ChrisHampshire]

If it's an issue with the valve block, they can be reconditioned as often it's just the O rings that need replacing. So a brand new one might not be needed.

Although, having said that, I believe the symptoms of this is usually the suspension sinking rather than rising....

 

[SLK230Auto]

Thanks Bud, no one seems to know anything conclusive about this symptom!
All i can think is that as the car is parked, locked and the electrics are 'disabled' then the only way air can get to the struts is from the air reservoir, through the valveblock and then to the struts - theres no other way. As soon as i unlock the car, the electrics enable, the car level sensors kick in, realise it's too high and vent air thus dropping the car to its correct height.
Think i'll bit the proverbial and buy a new valve block and see how it goes..will report back once fitted.

 

[SLK230Auto]

...meant to say that it will actually sink but only if the car is unlocked and the engine is not started; this allows what appears to be a faulty valve block to leak air to the struts, these rise, the level sensors kick in and lower the car by venting the air to atmosphere. The air reservoir is still in circuit so as the faulty valve block continues to leak air to the struts, the sensors correct and on it goes until the air reservoir is depleted. I t never gets that far though as i unlock the car, start the engine and drive off!