F11 Air Suspension Sticky thread

There was a great Sticky on checking and replacing the valve block, compressor etc which I think I may need to refer to one day (both airbags already replaced so valve/compressor is next!)

I cant recall which user posted it - but if they still have an offline copy of it it'd be great to have it posted again for reference.

Thanks

Stuart

 

I think the time has come where I might be looking at compressors etc?!

A few times over the last 10 days I've set off and on the first slight bump the kids have nearly hit the roof - the car has sunk to the stops on BOTH sides.

Given its both sides I'm guessing its unlikely that both airbags (replaced with cheap aftermarket over the last 3 years) have failed at the same time.

After a while it seems to reinflate to the right level and then stay there for days. I cant hear any hissing.

Does anyone have any resources around the valve block and compressor please?

As I've understood it, there are 2 airbags, valve block, compressor and ride height switches on ball arms - are there 2 of these, 1 each side or just on 1 side ?

 

F11 chassis and suspension technical training document listing components:
http://www.londonroadgarage.com/images/F11 Chassis and suspension.pdf

And the Arnott website has some useful installation pdfs e.g.
https://www.arnotteurope.com/produc...10-14-bmw-5-series-f07-f11-left-or-right.html

http://arnottinfo.com/manuals/P-2985.pdf

BMW say compressor relay must always be replaced when fitting new compressor unit and that rear air suspension struts should be replaced if car has been driven whilst bottomed out. ISTA service functions needed to calibrate ride level height once parts have been replaced.

 

Thanks - some useful stuff there.

I cant yet work out what part is at fault.

This morning the car was sat at the correct height - from last nights drive home. I started the car, it stayed up. I set off down the road and before I know it, its deflated both sides and bouncing along on bump stops.

It then stayed that way all the way to work, he last 2 trips its reinflated within 2 miles - on arrival I closed the car and reopened it, I could then hear the compressor for a minute or so but no change in ride height.

I'll start dismantling things tomorrow. But so far....

• The bags will hold air. Both sides drop at the same time. = to me the bags are ok - otherwise it would be intermittent on 1 side only.
• I've heard the compressor running - so power and control going to it.
• Green relay in boot near battery - looks intact and dry - no sign of water in the battery well.

So something triggers the system to dump all the air :-

• So it could be the ride height sensor (I think there is 1 on each side) so unlikely that both would be broken at the same time to cause both sides to drop.
• Which only really leaves the solenoid valve or the control unit I guess?

I found this interesting read on the logic in the control unit :-
http://www.micro-tronik.com/learnin...eneral-information/self-levelling-suspension/

And this overview
https://www.newtis.info/tisv2/a/en/f11-520d-tou/X8rcmqQ
and the wiring diagram
https://www.newtis.info/tisv2/a/en/...nsion/electronic-ride-height-control/EDfI5f6U

 

Ive got to the valve - disconnected the red and blue air lines. A small amount of air was released at this point but nothing significant.

The compressor runs when called - I can feel air from the ports on the valve - put I can easily cap it with my finger and feel very little if any pressure building up.

My theory now is the compressor internals have failed so its not building up any pressure and not enough to inflate the air bags? It must need a fair bit of pressure to lift the car up ?

Can anyone offer any advice on this theory?

If that is the issue then I guess its either try a compressor internals repair kit or new compressor time ?

 

As a further update:-

I've disconnected the output hose from the compressor to the valve block and then connected a manual bike trak pump. Ive removed the 40Amp fuse (182) so the pump doesnt run. There is solid resistance at this point against the handpump. If I unlock the car and open the boot to trigger the solenoid to demand air to pump up the bags, then the pump will pump, I got it to 40+PSI before I then whipped out the fuse 152 which closes the solenoid valve block thereby keeping the air in the bags.

Result is the car is staying up at present - but cant adjust itself. That to me says the valve block is ok, the solenoids when powered down are normally closed to seal the bags shut, only opening when a bag needs to go up or down.

Which brings me back to the compressor. I've removed it, opened up the piston chamber and the piston seal looks ok. I've opened up the air drier chamber and nothing looks untoward in there. Which leaves the discharge valve - that looks like a small motor on the back of the compressor.

Current theory is either the compressor isnt compressing enough anymore and the air is just leaking out through it - or the discharge valve is either stuck open or the control unit is telling it to open. I guess the control unit could tell it to open if the ride height sensor was broken and though the car was too high.

 

Ive messed with ISTA today - and on its recommendation - the resistance of the discarge valeve when measured is 11 ohms - supposed to be between 10 and 30 - so I guess thats ok.

The voltage on the discharge valve is 5.37volts - I cant find out what that indicates yet- is it saying open or closed?

I'm still of the opinion the compressor - despite the seals looking ok- just has lost its beef - hencewhenits pumping its actually letting air out - I can hold my finger over the outlet and there is little force on it to et air escape - I reckon it'd struggle to fill a baloon let alone an airbag.

Given Ive had no replies to my rantings - am I talkign to myself or can anyone offer some experience to help me along ?

Thanks

Stuart

 

I’d suggest revisiting the airbags As your findings suggest the compressor and ride height sensors are functioning correctly (allbeit with perhaps intermittent fault)
It’s not uncommon for “new” bags to leak (as I believe @Peter experienced)
Whether perished, worn or leaking at the clamp, I’d be inclined to remove and check fully, otherwise soak with soapy water and thoroughly inspect It may also be worth reterminating the connection at the airbags

It maybe worth checking the ride height sensor connections for water ingress, break the connections and spray wd40 after inspecting the pins, also disconnect the mounting and work the sensor up and down to ensure it’s not fouled with debris.
Thereafter, contemplate a compressor redress or change, though admittedly, it is odd that both sides are going down, so does suggest compressor fault

 

I'm seem to recollect that one mode of compressor failure can be that it seems to function correctly but there is no pressure.

It sounds like that's exactly what you've diagnosed. Although putting your finger on the end of a compressed air line can be very dangerous, see here https://knowledge.silvent.com/uk/dangers-of-blowing-with-compressed-air

There are some relatively cheap compressors out there now (under £200), I don't know how long they might last though.

 

I am no expert here but asked my colleague who had the same at work on his 230k 55 plate 525d at around 130k...,
The compressor was running, but it gets its air supply from the rh (?) wheel arch via a hose and small in line filter....
all the crap ingested from the wheel arch had collapsed the inlet pipe and his filter which had broken up and gone into the compressor.... it was running but was sporadic in its output.... ( the discharge valve is also part of the compressor... )
( you have had your compressor in bits and reckon it’s ok... so..???)
He suggests that’s what he’d go for.. changing the compressor...
I cannot help more.... his has been fine since for the last 100k...


Sent from my iPhone using Tapatalk

 

Final Update ....

It was the discharge solenoid valve in the end that was faulty. This is part of the compressor assembly, you need to take the compressor piston head off to get to it.

It had failed and was therefore set to permanent discharge - this wasnt a problem until the system triggered the solenoid valve block to open and the pump to pump, which should then close the discharge valve and fill the air bags. But without the discharge valve closing it was a fruitless task and the air just gushed out.

The discharge valve - isnt really a listed part, its got a Wabco number of 442 051 021 1 on and I managed to get one on ebay from Germany for about £60 delivered, much cheaper than whole new compressor block. I imagine any garage would have just replaced the whole compressor.

A couple of useful facts I discovered along the way :-

The discharge valve is normally closed, applying and holding 12v opens it. On a raise operation - the control unit sends a quick 12v pulse to open and reclose the valve, on a release operation it just holds it at 12v to keep it open.

If you need to raise the car and the system is stuffed - then I disconnected the black air hose from the compressor to the valve block, attached a bike track pump. Opened the boot to trigger the system to call for air to raise it, the valve block then opens to allow air to fill the bellows - pump like fury on the pump until at about 6 bar pressure the ride height sensors trigger the pump to stop and the valve block to close. Then disconnect the bike pump and take the control unit fuse out - you'll get a ride height warning on the dash but you get used to it after about a month. At this point you can actually remove the compressor from the car leaving the solenoid valve block under the car - disconnect with 2 screws.

There is a pump piston repair kit available from 4x4airseals - really helpful guy and in the process of elimination I fitted a new piston ring.

All in the cost was about £100 to fix. This is on top of the airbags replaced previously on both sides - what a shoddy system !

 

Well done, I admire your persistence to get to the right solution.

Peter

 

I have a BMW X5 xDrive30d F15 model 2015
I have the same issue
Can some one help me which fuse if removed will make the selenoid block valve stop working
Also I guess there is no separate fuse for the discharge valve ? If the compressor fuse is removed will the discharge valve will stop operating ??

also is there a non electrical mechanical way to close the discharge valve so that diagnosis can be accurately done ?

 

Having read through many forum posts on this subject, yours rang true as the symptoms were the same as mine. It also helped that it was so comprehensive and carefully written.

Unfortunately the cure, being the replacement of the discharge valve was short lived. I had a few weeks without issue but the problem has returned.

This morning I set off at correct height, only to have the back end drop after about 3 minutes. I pulled over and opened the boot, at which point it came back up to level.

Have had any further issues since your post above?

Thanks

 

Thankfully that part of the car hasnt given me any trouble since.

 

Well that's good. Glad you solved it.

I'll keep thinking.

 

Ive just had a browse through the forum and the amount of issues with air suspension is pretty scandalous !

 

Agreed. Looks like I'll go for the disconnect option for a while for the sake of my sanity, then keep trawling.

If I do solve it, I'll be sure to post an update.

Cheers Stuart.

 

Long shot coming back to an old thread but am struggling to find a genuine Wabco solenoid valve anywhere so hoping you are still on the forum and can remember who yours came from. Thanks.