BimmerFest BMW Forum banner
1 - 20 of 22 Posts

·
Registered
Joined
·
60 Posts
Discussion Starter · #1 · (Edited)
After some strange behaviour on my Air Suspension, I decided to post my findings here.

After replacing air springs, DIY here, my leaks were definitely gone (suspension would stay up for weeks rather than deflate after ~1 day). However, the suspension continued to act strangely - could release all air soon after starting the car\journey causing the rear to drop and terrible ride. Then on next start-up, would fill the springs and all could be well for days… Finally, the rear dropped and wouldn't go back up again despite the compressor being heard running.

Compressor and valve system:





First thing I checked was that air was reaching the solenoid for left & right spring control. First thing, I disconnected the pneumatic tube from the valve.



When the compressor ran, air was coming out but I could easily stop it by just placing my finger over the opening. The compressor unit was certainly not delivering the required 10~15 bar of pressure!

The OEM system is by WABCO. I removed the compressor unit expecting to find everything welded together but to my pleasant surprise, it is very serviceable!!

If you wish to dismantle:

Remove the 3 bolts connecting the assembly to the bracket. You can leave the cables connected. You just need a little room in order to remove the Air Dryer & connections.



Now you can release the 2 bolts connecting the Air Dryer to the Compressor. Note, there is a spring inside with quite a lot of tension so you need to back both bolts out a couple of turns each until the parts separate.



Spring that sits between the Compressor and Air Dryer



View inside the Air Dryer



O-Rings that you need to take care of. I left #1 in the compressor housing but placed #2 over the pipe on the Air Dryer for reassembly as thought less likely to damage the O-rings that way.



There is no point removing this cover as there is nothing serviceable inside (but you can remove the 3 x T25 Torx if you wish to take a look)



If you want to remove the compressor, remove the 2 T30 bolts and lift compressor housing straight up.



Housing from underside:



Piston connected to motor:



A component you can check and clean is the spring valve behind here.



The last component and the cause of my particular issue is the Discharge valve. Remove the two T25 screws and carefully prise\lift the valve up out of the Air Dryer unit.



Here is the view inside the Discharge Valve housing area. When filling the suspension air springs, #1 is blocked by the solenoid. When releasing air from the suspension air springs, the solenoid allows the air to pass from #1 to #2



And here, a picture of the valve. As you can see from the pneumatics schematic below, this is item #11 and is normally-closed, that is, the air in (blue) should not be able to escape (red).



My issue was that the valve was stuck open which is the discharge operation and lets:) air out of the suspension air springs.

My troubleshooting involved:

Checking the solenoid: ok



Blowing into the top-middle of the valve (blue) showed that air was passing through the valve (red).

I then connected the solenoid to a battery using crocodile clips and couldn't hear anything move. Air could still pass through the valve.

Sprayed a small amount of penetrating oil into the top\opening of valve and then exercised the valve on\off using the battery. A clear "clicking" could now be heard and with power off, the valve was shut, as it should be.

Put everything back together and all seems well.

New solenoid now on order (€25 on eBay) but car can be used in the meantime :)

With NewTIS down, here's some useful info which I had to catch with my phone:





 

Attachments

·
Registered
Joined
·
3 Posts
Thanks mate. Lots of good information here. I had the exact same problem. Lubing the dump valve worked for me....but a few days later the fault happened again. This time it wouldn't correct itself.
It's really horrendous driving with no air in the rear suspension. Even on good roads it becomes a real bone shaker!
Replacing the dump valve with a new valve from ebay solved the problem.
My advice.... don't mess about. Fit a new replacement, or end up doing the job twice!
 

·
Registered
Joined
·
1 Posts
This is great.
I have a BMW X5 xdrive30d F15 model 2015
I have been struggling with this problem for several weeks and my garage mechanic ( my friend) is baffled too.
I will try experimenting / cleaning the discharge valve. Replacements in india is not easy.

Are there dedicated fuses to disable the discharge valve, selenoid valve block and compressor ? what are the fuse numbers for my model ? I know the selenoid valve and compressor has dedicated fuses but i doubt if the discharge valve has something independent.
If there is a fuse for discharge valve, i plan to remove it and test for several weeks.

Mechanically too, its not possible to separate/permanently close the discharge valve ( I guess)
 

·
Registered
Joined
·
60 Posts
Discussion Starter · #7 ·
Hi
It'd depend on your model but I don't believe there's an independent fuse for the discharge valve.
The valve should be "normally closed" (inflate position) if working correctly so disconnecting the solenoid electrical connector would do the same thing as pulling fuse. You could also block the valve itself with glue I guess. I'm not sure it makes sense to do that however:
1. Likely generate a fault on EHC control unit.
2. If the EHC unit remains operational and decides it's necessary to lower the suspension, it would actually over inflate because the compressor also runs when in discharge (lowering) mode.

Have a look at the discharge valve first and see what you find. Even if you can free it up with penetrating oil, it'll only last weeks/months before it starts to act-up again.
Replacement and a normally operating system is the way to go if at all possible.
Let us know if you find a work-around though.

Could also try pulling the main fuse to EHC and see what happens - F122 in above F01 diagram - fuse board in the trunk/boot.
 

·
Registered
Joined
·
280 Posts
Excellent and helpful write up!
thank you for sharing with the community

I was wondering if you can check my thread whenever you get a chance


basically, my car was low on Tuesday, horrible ride when driving. did some quick research, saw a video on YouTube that suggested to check a fuse. one 40 fuse was blown. Replaced with a new one and car went back up. Currently have it connected to a noco genius 10 to charge up the battery.

im trying to figure out what triggered the fuse to blow?

thank you for any help or advice that you can suggest
 

·
Registered
Joined
·
4 Posts
After some strange behaviour on my Air Suspension, I decided to post my findings here.

After replacing air springs, DIY here, my leaks were definitely gone (suspension would stay up for weeks rather than deflate after ~1 day). However, the suspension continued to act strangely - could release all air soon after starting the car\journey causing the rear to drop and terrible ride. Then on next start-up, would fill the springs and all could be well for days… Finally, the rear dropped and wouldn't go back up again despite the compressor being heard running.

Compressor and valve system:





First thing I checked was that air was reaching the solenoid for left & right spring control. First thing, I disconnected the pneumatic tube from the valve.



When the compressor ran, air was coming out but I could easily stop it by just placing my finger over the opening. The compressor unit was certainly not delivering the required 10~15 bar of pressure!

The OEM system is by WABCO. I removed the compressor unit expecting to find everything welded together but to my pleasant surprise, it is very serviceable!!

If you wish to dismantle:

Remove the 3 bolts connecting the assembly to the bracket. You can leave the cables connected. You just need a little room in order to remove the Air Dryer & connections.



Now you can release the 2 bolts connecting the Air Dryer to the Compressor. Note, there is a spring inside with quite a lot of tension so you need to back both bolts out a couple of turns each until the parts separate.



Spring that sits between the Compressor and Air Dryer



View inside the Air Dryer



O-Rings that you need to take care of. I left #1 in the compressor housing but placed #2 over the pipe on the Air Dryer for reassembly as thought less likely to damage the O-rings that way.



There is no point removing this cover as there is nothing serviceable inside (but you can remove the 3 x T25 Torx if you wish to take a look)



If you want to remove the compressor, remove the 2 T30 bolts and lift compressor housing straight up.



Housing from underside:



Piston connected to motor:



A component you can check and clean is the spring valve behind here.



The last component and the cause of my particular issue is the Discharge valve. Remove the two T25 screws and carefully prise\lift the valve up out of the Air Dryer unit.



Here is the view inside the Discharge Valve housing area. When filling the suspension air springs, #1 is blocked by the solenoid. When releasing air from the suspension air springs, the solenoid allows the air to pass from #1 to #2



And here, a picture of the valve. As you can see from the pneumatics schematic below, this is item #11 and is normally-closed, that is, the air in (blue) should not be able to escape (red).



My issue was that the valve was stuck open which is the discharge operation and lets:) air out of the suspension air springs.

My troubleshooting involved:

Checking the solenoid: ok



Blowing into the top-middle of the valve (blue) showed that air was passing through the valve (red).

I then connected the solenoid to a battery using crocodile clips and couldn't hear anything move. Air could still pass through the valve.

Sprayed a small amount of penetrating oil into the top\opening of valve and then exercised the valve on\off using the battery. A clear "clicking" could now be heard and with power off, the valve was shut, as it should be.

Put everything back together and all seems well.

New solenoid now on order (€25 on eBay) but car can be used in the meantime :)

With NewTIS down, here's some useful info which I had to catch with my phone:





Great write up. I have the same issues with my F15 X5 the suspension started dropping whilst I was on holiday but it kept resetting itself until I got home When the next day it wouldn’t inflate at all. I pulled the assembly and found the dump valve was stuck so I replaced it. The system still won’t inflate and I now can’t hear the compressor running. I checked all the fuses and they were good so I got a new relay, still no power to the compressor. if I provide 12 volts straight to the compressor on the bench it runs good and has good pressure output. Do I now need to change the control module or is this maybe a software reset issue?
 

·
Registered
Joined
·
8 Posts
Great write up. I have the same issues with my F15 X5 the suspension started dropping whilst I was on holiday but it kept resetting itself until I got home When the next day it wouldn’t inflate at all. I pulled the assembly and found the dump valve was stuck so I replaced it. The system still won’t inflate and I now can’t hear the compressor running. I checked all the fuses and they were good so I got a new relay, still no power to the compressor. if I provide 12 volts straight to the compressor on the bench it runs good and has good pressure output. Do I now need to change the control module or is this maybe a software reset issue?
What did you replace your dump valve with - was it one of the copies from eBay or did you find an original Wabco one?

This is the best video I've seen explaining the whole thing including the rebuild and why they dryer ends up wet:

Don't skip on the disassembly of the dryer and drying it out, that's normally the reason that the solenoid valve fails - water from the dryer getting through to the discharge valve causing corrosion.

On my F11 the compressor doesn't start until I start the engine. It partially inflated when I opened the boot but had to start it to return to normal height.
 

·
Registered
Joined
·
4 Posts
What did you replace your dump valve with - was it one of the copies from eBay or did you find an original Wabco one?

This is the best video I've seen explaining the whole thing including the rebuild and why they dryer ends up wet:

Don't skip on the disassembly of the dryer and drying it out, that's normally the reason that the solenoid valve fails - water from the dryer getting through to the discharge valve causing corrosion.

On my F11 the compressor doesn't start until I start the engine. It partially inflated when I opened the boot but had to start it to return to normal height.
Thanks for the response. I’ve watched that video many times but it doesn’t help with my particular issue. I fully cleaned everything but there was absolutely no evidence of water in the system anywhere and the dump valve looked like new although it was stuck. I got the new dump valve from eBay as I couldn’t find a Waco one. my compressor used to start as soon as I opened the drivers door But now it doesn’t, even with the engine running.
 

·
Registered
Joined
·
8 Posts
Thanks for the response. I’ve watched that video many times but it doesn’t help with my particular issue. I fully cleaned everything but there was absolutely no evidence of water in the system anywhere and the dump valve looked like new although it was stuck. I got the new dump valve from eBay as I couldn’t find a Waco one. my compressor used to start as soon as I opened the drivers door But now it doesn’t, even with the engine running.
When I did the air springs on my old E39 last year, it wouldn't re-inflate when I re-connected everything. I had the diagnostic software on a laptop and used that with OBD lead to tell it to raise the rear suspension for 10 seconds I think it was, and that started the compressor, it raised and then started working. Have you tried jacking it up a bit to see if it triggers it? (Long shot)
 

·
Registered
Joined
·
8 Posts
If it were me:
Check the fuse on a multimeter as opposed to visual check (fuse 182 for the compressor) - sometimes fuses look ok but are not.
If fuse definitely ok, what about if you remove the relay - do you have 12V unswitched arriving at the relay?
Can you jump the unswitched 12V at the relay to the feed that goes to the compressor - e.g. apply 12V to the relay blade socket that goes to the compressor? Does that start it running? (careful if so, don't inflate all the way and risk over inflating)
 

·
Registered
Joined
·
10 Posts
Anyone know the exact bolt size, for the top 2 bolts of the cover over the compressor? I know the bottom 2 are 10mm

But I had to buy a wrench to reach the top 2, and I'm so mad they aren't 10mm lol. Like why would BMW do that? I don't want to buy the wrong size again
 

·
Registered
Joined
·
10 Posts
I was under mine at the weekend changing the discharge solendoid valve (for one of the copies I bought on ebay), those 4 plastic nuts holding the plastic compressor cover are definitely 10mm.
For the F02? No way lol, 10mm doesn't fit on the top 2. They're definitely smaller around 8mm maybe, trust me I tried it so many times.

Just not sure if they're 7,8,9
 
1 - 20 of 22 Posts
Top