Air Suspension Valve Block

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parranger

Member
Posts
59
Location
Near Durham, UK
I have been experiencing problems with the air suspension system on my 2001 P38. Rear end can unpredictably slowly deflate and very slow to recover so air pump replaced. The air bags now inflate quickly and can remain under pressure. But the rear end still unpredictably deflates. The valve block has been declared faulty and a good second hand replacement has been sourced.

What is the most likely cause of the Valve Block failure? I intend to fit the replacement block but rebuild the old block (if possible) ready to fit if required. Any advice would be welcome.
 
parranger said:
I have been experiencing problems with the air suspension system on my 2001 P38. Rear end can unpredictably slowly deflate and very slow to recover so air pump replaced. The air bags now inflate quickly and can remain under pressure. But the rear end still unpredictably deflates. The valve block has been declared faulty and a good second hand replacement has been sourced.

What is the most likely cause of the Valve Block failure? I intend to fit the replacement block but rebuild the old block (if possible) ready to fit if required. Any advice would be welcome.
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More likely to be airbags leaking or even a height sensor. If it's the valve block a new set of O rings will fix it.
Also worth checking the connector behind the passenger side kick panel for corrosion and the connectors in the EAS box for loose connections.
A blown exhaust can also melt the pipes causing pin hole leaks.
 
Nothing wrong with servicing the valve block but i doubt that it is the cause of the rear dropping. Only two things in the valve block can cause a corner to drop providing the pipe connections are sound. That is a leak past the small O'ring at the base of the solenoid seat or the seal on the bottom of the solenoid shaft itself. Leak from this usually caused by a crusty build up of desiccant from a failing drier. That should effect all corners so if just the rear drops look for a leak in that area. Would think compressor failed feeding a leak.
 
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Datatek and wammers Thanks for your comments. I had thought that the source of the leak would be in the rear end but the garage has checked this area and could find nothing wrong. If the rear end drops then pumping the vehicle up to the maximum will hold the suspension overnight without loss of pressure. This has led to the valve block being suspect. Reasoning that if the higher presure holds then the problem must be in the valve block .. is this a reasonable argument?
 
Another test is to unplug the relay which is under the passengers seat. This stops the self levelling so if its down in the morning then the leak is in the rear bags.
 
parranger said:
Datatek and wammers Thanks for your comments. I had thought that the source of the leak would be in the rear end but the garage has checked this area and could find nothing wrong. If the rear end drops then pumping the vehicle up to the maximum will hold the suspension overnight without loss of pressure. This has led to the valve block being suspect. Reasoning that if the higher presure holds then the problem must be in the valve block .. is this a reasonable argument?
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Unlikely to be valve block but refurb it if you want and see what you get. Odds on it will still drop. Extra pressure against the small base O'rings could effectively seal them but unlikely. But if solenoid seat valves are leaking extra pressure against them would certainly leak past them. Nothing else in the valve block other than the actual pipe connections will cause a corner to drop.
 
Think I am with Datatek on the air bags? how old are they? Garages don't spend much time looking at slow leaks so don't rely on that. Our local B&Q sells a spray tin of gas detection spray for about a fiver. Put the car on high setting and spray the air springs, and any connectors up to and including the areas aound the EAS Box as Wammers says if you see any bubbles thats the leak and don't forget the connectors to the air springs themselves. Also see if the air bags are in good condition? at lower settings etc.
Datatek mentioned that an exhaust leak can melt the air line - this will be above the rear axel in the middle where the rear exhaust joins and rots with age.
 
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Thanks for the comments guys. Must admit that my gut feeling is that there is a problem at the rear end of the vehicle. The strange thing is that it is always both sides of the rear end that drop. Some days the suspension does not drop and at other times I can ride round the block and on stopping the car the rear end drops! This problem started a few weeks ago following a big freeze up when the car dropped to the bump stops overnight and could only be raised with difficulty. The max height could not be achieved hence the decision to fit a new pump. The pump was the original one fitted to the car in 2001 so I didn't give this much thought . I agree that this could have been a result of the old pump having to feed a leak.

Before the big freeze there was no indication that there was a problem the car is used daily and when started the ride height was there and ready for moving off without any pump action. Air bags were changed about 4 year ago. Obviously there needs to be more checks done to find the cause.
 
Four year old bags! if Dulops this could be the problem I had to replace mine at about that time (I do high mileage and live close to the sea but don't know if that has any effect). Some people have bags that have lasted eight or more years?? As Datatek says full height setting could seal a leak but I was sugesting you spray and inspect the bags at all settings.
 
stopover said:
Four year old bags! if Dulops this could be the problem I had to replace mine at about that time (I do high mileage and live close to the sea but don't know if that has any effect). Some people have bags that have lasted eight or more years?? As Datatek says full height setting could seal a leak but I was sugesting you spray and inspect the bags at all settings.
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Four years:eek: Makes my Arnott's sound an even better investment, over 5 years now and still look like new:D
 
parranger said:
Thanks for the comments guys. Must admit that my gut feeling is that there is a problem at the rear end of the vehicle. The strange thing is that it is always both sides of the rear end that drop. Some days the suspension does not drop and at other times I can ride round the block and on stopping the car the rear end drops! This problem started a few weeks ago following a big freeze up when the car dropped to the bump stops overnight and could only be raised with difficulty. The max height could not be achieved hence the decision to fit a new pump. The pump was the original one fitted to the car in 2001 so I didn't give this much thought . I agree that this could have been a result of the old pump having to feed a leak.

Before the big freeze there was no indication that there was a problem the car is used daily and when started the ride height was there and ready for moving off without any pump action. Air bags were changed about 4 year ago. Obviously there needs to be more checks done to find the cause.
Click to expand...

Think it maybe an idea to check the system for moisture.
 
Castor said:
Bloody kids.....

I was past it - 30 odd years old by then - I did my festivalling in the early 70's - Glastonbury, Windsor, Watchfield, Stonehenge and so on....
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Last time Keith and Mozz Smith went to Stonehenge they still did sacrifices. :D:D:D
 
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