different air suspension pain 4.8is

pieter4458 · #1 09-11-2012, 12:51 PM

I have a X5 4.8is with the famous two axle air suspension. My issue is not the normal compressor, leaking bags or control unit errors.

The problem with the car is that when parked the front drops about 10-15 mm and when start it wakes up to normal height (even if parked for 15 minutes).

I opened up the concentrator tank, checked the pipe links with soapy water, as well as the pressure regulator - no leaks. It also goes into air suspension inactive mode from time to time and then it has to be reset. No major errors on the computer when reset.

How do i fix this?

Any suggestions?

TwinsPoppa · #2 09-11-2012, 12:58 PM

If it drops at ANY time, I would start with inspecting the air strut bags and connections for leaks. How do you know its not the air struts?

Then if that checks out. I would start looking at all the other components.

SlickGT1 · #3 09-11-2012, 01:07 PM

Quote:

Originally Posted by pieter4458

I have a X5 4.8is with the famous two axle air suspension. My issue is not the normal compressor, leaking bags or control unit errors.

The problem with the car is that when parked the front drops about 10-15 mm and when start it wakes up to normal height (even if parked for 15 minutes).

I opened up the concentrator tank, checked the pipe links with soapy water, as well as the pressure regulator - no leaks. It also goes into air suspension inactive mode from time to time and then it has to be reset. No major errors on the computer when reset.

How do i fix this?

Any suggestions?

LOL. How exactly did this exclude the leaking bag as the problem? Mix some soap and water, put into one of those spray bottles, and spray the crap out of that bag. I bet it is leaking.

pieter4458 · #4 09-11-2012, 01:20 PM

I recon that if both air bags goes down simultaneously it can not be them and suspect the lines. But it can happen that they are both bad and will test with soapy water.

civdiv99 · #5 09-11-2012, 06:08 PM

Rear bags are independent but fronts do have lines in common. Start checkin' connections from the accumulator (ok, it's an air tank) under the car on fwd.

Quote:

Originally Posted by pieter4458

I recon that if both air bags goes down simultaneously it can not be them and suspect the lines. But it can happen that they are both bad and will test with soapy water.

pieter4458 · #6 09-12-2012, 07:38 AM

I checked the two front lines at the control valve, next to the accumulator and could not find any leaks. The next step is to check the line connection on the top of the airbags for airleaks. If there is nothing, then the only culprit can be the airbag itself that is leacking (slow puncture).

I am afraid to use the car at this moment as the movement on the airbag can sqeeze air through the small punture and the pump keeps on working to compensate - it may burn out.

What puzzles me is why is the car dropping in front to a certain level and then it settles. Can it be that the small hole in the bag folds to a point where it seals and why both sides?

TwinTurboGTR · #7 09-12-2012, 07:51 AM

Bingo. I am sure if you left the car sit for 48 to 36 hours, the system would be completely slammed.

TwinsPoppa · #8 09-12-2012, 11:57 AM

Quote:

Originally Posted by pieter4458

I checked the two front lines at the control valve, next to the accumulator and could not find any leaks. The next step is to check the line connection on the top of the airbags for airleaks. If there is nothing, then the only culprit can be the airbag itself that is leacking (slow puncture).

I am afraid to use the car at this moment as the movement on the airbag can sqeeze air through the small punture and the pump keeps on working to compensate - it may burn out.

What puzzles me is why is the car dropping in front to a certain level and then it settles. Can it be that the small hole in the bag folds to a point where it seals and why both sides?

The leak may be so miniscule, for now, that your last point is what's happening.

As for why its leveling on both sides, it just may SEEM to be both but can be only ONE having the leak.

Here's why, after 6 hrs:

Wake-up
In wake-up mode, the control unit is woken up for a set period of time in order to compensate for possible inclination of the vehicle. Inclination of the vehicle can be caused by large temperature differences or by minor leaks. Adjustments to the front and rear axles ensure that the vehicle is visually level. To minimize power consumption, the vehicle is lowered only. The nominal level of the lowest wheel serves as the nominal level for all other wheels. The lowest nominal level to which the vehicle is lowered is the Access level (-35 mm).

IMO, I think there's nothing else going on here but a leak in one of your air struts.

SlickGT1 · #9 09-11-2012, 01:56 PM

Do the same to the lines. Spray all the connections with soapy water. Watch for bubbles.

TwinsPoppa · #10 09-11-2012, 02:08 PM

Well, let's see here are the components of EHC2.

- Ride Height Sensors (x4)
- Air Suspension (air springs/struts)
- Air Supply Unit (compressor, 3 valves and a drier)
- Pressure Accumulator/Valve Unit (under vehicle)
- EHC2 Control Unit (behind the glovebox)
- Switch (ride height)

It seems like you have a leak somewhere. If not, it would definitely help to have it scanned by a GT1 and follow the test plan(s). Otherwise, could be tricky finding the root of your problem.

Meanwhile, let's see what others say and do some searches.

I wonder if the Pressure Accumulator can have a valve stuck a little open?