andyman32

Hi, have an '08 A8L. Since I bought it a year and a half ago, when I let it sit for roughly a week or more, I get the green 'low suspension level' light and the car raises itself. Recently I've noticed it - intermittently - when parking even for as little as an hour; sometimes it can be parked for 2 weeks and maintain a normal level. Sometimes I notice while driving it that periodically, stopped at intersections, the front will raise itself a bit. As I observed very carefully, on different surfaces, parked uphill, downhill, level surface, it's ONLY the front-right that sags. The most clear example to date is when I jacked the front-left of the car a few weekends ago. When I lowered it to the ground, the front right wheel was scrunched up in the wheel well, about 1" from the top of the fender.

The odd part: it only appears to be that corner.
It will settle less than 1/2" at most, but never more than that (prior to that weekend when I jacked the opposite side of the car)
It never settles all the way up into the wheel well. However much it's going to settle, it settles that much, then remains at that level.
Last week I was driving and observing the level across the hood (using the ground as a point of reference) and saw that the front-right corner of the car actually LOWERED itself slightly while waiting at an intersection.

I'm stymied. The compressor appears to work just fine re-establishing the correct level of the car. The front-right air spring seems to be the only one that settles... but it does not do so consistently (sometimes it does, sometimes it doesn't), and it never settles all the way up into the wheel well.

If it were an actual air leak, it should be a leak. Slow, fast or otherwise, air should continue to leak out until it's depressurized. If it settled 1/4" after 3 days, I'd expect it to settle 1/2" after 6 days and 3/4" after 9 days (or whatever, adjusting the rate for residual air pressure left in the system).

If it were a bad ride height sensor, it should have no effect on the level of the spring while the car is turned off and sitting for days.

Whatever it is, it has to be effecting only that corner. Not the entire system, not front wheels / rear wheels, just that corner.

This makes me believe that there must be some kind of pneumatic pressure regulator associated with each corner, a physical valve. Perhaps one that's sticky, intermittent, maybe effected by temperature or humidity (although that also would not be consistent). Perhaps it is in the valve block?

Does this make sense to anyone? Any thoughts what could be going on? I was about to buy a new air spring, but based on observations I'm pretty well convinced that won't fix it. There must be some kind of blow-off valve in the system but I don't have documentation that describes the system in enough detail for me to figure out what might be the culprit. I do have Ross-Tech VCDS.

Thanks in advance for your ideas!

Brozee

Sounds like you just have one leaking strut. All struts pump up to a certain specified level. I think you may be overthinking it and it is just one

ltooz_a6_a8_q7

May be the bag isn't the issue, it's the air connector needs to be reseated, sometimes it seals and sometimes it doesn't... may be a simple fix.
Don't replace anything that's not confirmed and tested.
Valve Block will lower both front or rear, seldom individual.
Cheers,
Louis

SS_RTR

It is possible that the good strut on the left and the front stabilizer may be taking the pressure off the right strut so that it doesn't continue to leak down all the way. There are several threads on hear about soapy water test that you can do around the bottom of the struct and air line connections. Consider disconnecting the front stabilizer and putting in jack mode via MMI to isolate that right strut. That compressor may be working well now, but the more it runs, the more it wears.

andyman32

I think it is just a leaking strut. It seems to be leaking down more quickly now. Good point about the stabilizer bar potentially keeping one side from going all the way down relative to the other. I have sprayed it down with soapy water and found no bubbles whether under load or not; of course, if it's leaking more regularly now the leak may show up more clearly. Worth another try before ordering a replacement.

Jack88

Did you spray the top of the strut where you have to open the hood? There are a couple rubber pieces you have to pull back, but hey.

andyman32

Good pointer - tried that today, no dice. I did spray as much as I could reaching in to the wheel well. The connector at the top of the strut clearly isn't leaking. I may try to get it up on ramps this weekend and spray the strut from beneath while under load.

At this point I'm pretty well assuming it's just a leaking strut though. Relatively straightforward.

Jack88

All soapy water tests should be with a filled strut under load! Ramps help a lot, hard to get in there without them.

andyman32

Oh yeah - wow - definitely none of that going on up on top there, on my car.

Mx-3GSR

so I just tried to rebuild mine
I bought new "O" rings and put it back together and it still leaks

not sure how the bag is constructed with the aluminium but I think mine leaks from the center where the top of the strut goes though and the nut goes on (it must be 2 parts there)

does that make sense? Im pretty sure the O ring is seating properly I think its the bag it self