Mae

So, I've talked to several people about this, and we haven't yet figured out what's going on. My '02 allroad is lower on one side, both front and back, and my compressor seems to run too frequently. To be clear, the car is NOT LOWERING when sitting. I measure it when I get out of the car, and it's the same when I come back in the morning, but one side is about 1/2" - 3/4" lower than the other side. The slight variation seems like it is likely just relating to how it's been adjusting during a drive, but it's stable where it sits, and doesn't appear to be leaking at all.

Arnott air bags have already been put in front. Audi bags are in back, and seem fine. There were NO FAULT CODES in the suspension when it was scanned last week, when I initially asked about the problem. They looked at the suspension and saw nothing obviously wrong, but the Audi specialist guy at my shop is away for three more weeks

Suggestions have been that the suspension could be needing to be re-calibrated, having had some suspension work done on it over the years. But, could that explain the frequency of the air compressor running? Perhaps it's constantly trying to adjust itself if not correctly calibrated, and 'confused?'

Another suggestion is that the air compressor is running too frequently because it's getting weak. It is a bit noisy, so I believe that I will need to replace it at some point in the not-too-far future. But, why would that cause it to fill the bags less on one side of the car?

Another possibility that was mentioned is the valve body that is next to the compressor. I was told that this could perhaps have a blocked valve(s), but don't know a way to test/check that. There are 6 lines coming out of the valve body, and only 4 air bags, so I don't know what the other 2 lines are.

I suppose there could also be a leak in an air line. I don't know if there are any lines that would be shared for both the front and back on one side of the car.

I'm trying to figure out as much as I can about this problem before I bring it to a shop to have them spend a bunch of time diagnosing it, which will cost a lot, before even getting to the repair.

ezveedub

You may need to check the ride height values in the control module and possibly perform a calibration. Also, make sure the rear shocks don'y have a leak, as I have seen the oil go from the air spring, into the valve body block, so you may want to check that also. The pump will eventually get weak and if its running a lot, there is most likely a leak. That's what wears out the pumps.

Mae

Like I said, there does not seem to be a leak in the rear air springs. The car IS NOT lowering, and it's not just lower in the rear, it is the front and rear of one side, but stable. I know that leaking air springs cause the pump to run a lot, and will cause it to wear out, but a weak pump in itself can cause it to run more frequently if just running less effectively, I've been told. Calibration being off could potentially cause it to run more frequently to be constantly adjusting, perhaps? Mechanics don't seem to be sure about that.

So, how would you check the valve body block?? That is one of the possibilities I'd like to check, but don't know how to check it.

Another possibility that sounds feasible is a leak in a line going to the air springs.

ezveedub

Leaks in the line are very simple to check for. You just have to jack up the car, disconnect the line at the shock and valve body, cap one end and apply vacuum with a vacuum pump. It should should hold vacuum indefinitely. If not, it's bad. I would check the the calibration though to make sure its not been calibrated incorrectly first though. If you find oil in a line, you know a shock has a blown seal and it's pushing it into the valve body. The rears are know for this, since the lines attach at the bottom, while the fronts are at the top.

slatebrick

This would seem like a long shot, but could the right height sensor brackets be incorrectly installed, or bent? It would seem very unlikely that they would both be wrong on one side. Has this always been the case with this car, or is this a new problem?

Mae

Hmm . . . I don't even know what a vacuum pump is, but I assume it's something that an auto shop has and I don't Anything I can substitute? I also have no way of checking the calibration, as I don't have a VAG COM, but is this a quick thing for them to check if I bring it to the shop, or do they just have to re-calibrate it? I think they wanted ~1.5 hrs to do this.

I still think, since it's both front and rear of one side, that it's likely not the air bag. Any way to check the valve body though??

Mae

I'm not sure if it's new or not. I've had the car for about 5 months and just noticed it a couple weeks ago. It was up on a lift at the tire shop the other day and we looked at the sensors. Nothing was obviously different from one to the other. The compressor running more frequently has been more recent I think.

Also, does it store air somewhere? I raised it from level 2 to 3 a couple times and at least once I don't think I even heard the compressor, but it raised up. Maybe there was already enough air in the lines? Or maybe I just didn't hear the compressor but it was on.

5v/cyl

Yes there is a air tank in the rear hatch behind the drivers side panel.

A knowledgeable shop with VAG-Com can readjust it pretty easy and fairly quick. It's just typing values into a computer and measuring heights.

When you put it up on the lift at the shop did they or you put it into 'Jack
Mode' first? If not that might have messed up your height right there.

Mae

What is 'jack mode?' Is that when they press the ride height up and down buttons and hold them to lock air in? I think that it's probably been jacked up without doing this a couple times, but how would that mess up the ride height calibration?

Trying to visualize where this air tank is that you're describing. Under the car? I'm wondering why the compressor runs too frequently. Maybe a leak in a line going to that tank??

5v/cyl

Everything you need to know about the AR's air suspension: http://www.volkspage.net/technik/ssp/ssp/SSP_243.pdf

Open rear liftgate and open the panel just below the 12v power point. You will see the silver airtank in there.

Jacking up the car without putting it into jack mode first will cause the air to be let out of the air springs if it is still in active monitoring mode. The ride height module thinks the height is to high and tries to correct it by letting air out. As a result the car will then go way too low when taken off the lift or jack and this can mess up sensors and/or air bags.