rear corner air suspension sagging

[ninjajim4]

Hi all,

I've seen a lot of threads but none that really match my description. The driver's side rear corner is sagging. It's not blown because when I jacked it up to inspect, there is clearly some pressure in there, just not enough with the full vehicle load. It doesn't change height whether the car is running or not.

I checked all fuses, those are fine. I've also tried pulling the fuse in the trunk to reset the ride height, but all I hear is a small click and nothing happens.

I think it's most likely the compressor itself. However, I don't have any warnings on the dash or the message center. Is that typical or expected?

Based on other threads, I think I should be getting an error message. I don't want to just throw parts at it. This is for an 2008, 4.8 liter.

Thoughts?

Thank you!!

[ard]

Was it displaying sagging prior to this? Specifically it would drop after being parked, but then when driving it would pump up? If so, something was leaking and caused the pump to die.


Problem is that this isnt something that does well with checking fuses and guessing at parts. Do you have software to diagnose BMWs? I believe you can command the system to test the pump, for example.

[andrewwynn]

If sags when off but lifts when on it's almost surely the air spring.

Lift the car so the spring is stretched out and spray with soapy water. If no foam it's likely a leak on the line.

If the compressor is failed both sides will eventually sag and never lift.

If they lift asymmetrical, often it's the height sensor rod.

[bcredliner]

Originally Posted by andrewwynn

If sags when off but lifts when on it's almost surely the air spring.

Lift the car so the spring is stretched out and spray with soapy water. If no foam it's likely a leak on the line.

If the compressor is failed both sides will eventually sag and never lift.

If they lift asymmetrical, often it's the height sensor rod.

[bfeng]

Originally Posted by ninjajim4

Hi all,
doesn't change height whether the car is running or not.

90% it is your driver side rear right height sensor. It'll be obivious in 5 seconds when you look under the car for a rod connected to a black box via an arm that rotates as the suspension goes up and down. Either this sensor box is bad or the wiring/connector are bad. On my car, it was a wire that had been rubbed thru because it was touching the lower control arm. Splicing the wire back together saved the me cost of the ride height sensor. Anyway, fast/easy to change the sensors (part a bit pricey unless you get a used one off ebay), and helps to have a set of think small metric wrenches.

Good Luck

[bcredliner]

There are some instances when vehicle has been jacked up that a sensor arm will turn over to the other side. This will change the ride height but should also generate a air suspension warning light.