PaulW

So it finally happened to me at 89K miles.....today I see only the front end is down, but it's both the right and left hand side. I have never had to troubleshoot this before, but I would guess it might be a leak in the distribution lines to the front vs. a strut leak, or I should say "I am hopeful it is that".......will have to start researching it......

2004A8L

maybe not, if one side is leaking a lot it will bring the other side down too, let it air up and put it in jack mode and keep an eye on the car see which side starts to drop first.

MP4.2+6.0

As already mentioned, with leak in one side of front, both sides drop. You need to watch very carefully after shutdown and in ensuing hours or day to know which side the leak is on. Measuring from ground to fender on each side from start of checking can help to look for side w/ greater drop.

What you are fighting is the sway bar. That is transferring the weight difference across the two sides. If you are parked at home and can't be sure which side, you can disconnect sway bar fairly easily at the lower U shaped link. Only need to do one (either) side. Then which is the failing side should be more obvious.

ltooz_a6_a8_q7

My right side bag leaked @119k, both went down due to leveling system. The only way to find out if it's the valve block or the bag(s) to bring them both low is a simple test.
- Raise to lift.
- Put in Jack Mode and wait. Whichever side sags is the culprit, if both down then...
This is my thread at 119k miles.
Cheers,
Louis

PaulW

Thanks everyone. I could of sworn I have seen the left front dropping a bit over the past month or two (meaning I could see it raise when I would start the car), but you really can't see the right side.

I went out to the garage to run the compressor about 20 minutes before I had to go to see which side would go down/how far, and the pump never got it up to normal height before it tripped on thermal.

I will troubleshoot later on, lucky for me I have multiple cars and don't have to drive this for now.

Jack88

If it's leaking bad enough the pump can't fill it without overheating, see if you can actually hear which side is leaking. I could on mine when it failed.

PaulW

So based on my testing, the leak is at the top of the strut in the engine compartment via bubble testing). After searching the forums I found that the O-ring size for the top is 11 mm inside diameter by 2 mm width (which makes it a 15 mm outside diameter). It took me about 4x as long to get the tools for the job (41 mm that needed to be ground down to fit into the hole and a proper offset 18mm) than doing it.

I changed the upper and lower O-ring (lower O-ring was 3 mm width by 57 mm inside diameter, 63 mm outside diameter). It still leaks from the top of the strut assembly via bubble test, but it leaks less than before, and everything else in the system works correctly when I look at it via measuring blocks in VAG-COM.

After I looked into the assembly when I took it apart, the upper O-ring is at the same pressure as the whole assembly, i.e. the inlet air pressure hose is connected to the same chamber and the only thing that I can see that seals that chamber from the outside is the upper strut shaft O-ring. I do not see the failure mode at the present time.

Because this is such a quick job, I am considering getting the following O-rings: 2.5 x 11 ID, 3 x 11 ID or 2.5 x 10 ID or 3 x 10 ID and trying it again. For me, it's a science project now. Not to mention I have the only McMaster-Carr in Illinois about 5 miles away from me and can pick them up an hour after ordering.

Anybody have any thoughts?

Jack88

Did you install the o-ring dry? Did you clean both surfaces? I used motor oil to lube my o-rings when I installed them since they had to slide in a tight fit while being installed, not sure if you're supposed to do that or not! Mine doesn't leak at all, though, even after sitting for 2 weeks.

PaulW

I cleaned everything and used some synthetic grease on the O-ring when I installed it. Everything went back together well. I reviewed an O-ring seal guide and based on the size of everything I measured (strut OD at O-ring fit and width of cut out), the 2 x 11 mm is the exact perfect size for that application, so I don't think I have the wrong O-ring size. I just don't know it if leaks from the top via bubble test if the leak can come from somewhere besides the O-ring.

I used a Viton O-ring, which is a 75 duraometer hardness....wonder if it was too hard or if the airbag is leaking from somewhere else that causes it to bubble at the top.

At this point, I am thinking to just get the set of two new bags. The real reason I didn't do it first is that I had time over this weekend to try the O-rings and there was no way I was going to get the new bags this weekend.

This is the original O-ring, too lots of pictures, did not see degradation.



The following picture is replacement 2 x 11 (ID) O-ring, I bought Viton which is a little harder.

PaulW

After thinking about it last night, if the O-ring didn't fix it, after looking at pictures, there is another seal, so I figure it's leaking from this seal. Without figuring it all out, I ordered the replacement bags from ebay. I suppose I will take the black seal out once I have the strut installed. I was tempted by a S8 strut assembly with 80K miles on it that just showed up on ebay for $180, but I bought new.

Here is the seal I am referring to:




I was challenged to say the least to get the correct tools, so here's some of my tips. Somebody posted about a 41 mm at Harbor Freight, but when I went to my local store, I could not find a 41 mm, later I think I found one in a set, but it was a black impact socket. I quickly looked on Amazon and found I could buy one for about $11, so I bought it. So while I was waiting for it, I was at Menard's and figured out the 1 5/8" is 41.275 mm, so I know it would work just fine on the strut nut. After buying it, I figured out that it wouldn't fit into the hole. I measured the OD of both and the 1 5/8's was smaller OD, and this is after going to multiple places, this was by far the smallest OD socket I could find.

However, the 41 mm showed up, so I decided to grind that one down and return the Menard's 1 5/8" which was about $12 or $14. It took about 25 minutes to grind it down to size!



Final results:




Just fits, but that's good enough for me!




I had also bought an offset 18 mm off Amazon and it ended up that it did not have the proper offset, so it wouldn't fit into the strut, it would interfere with the top because the offset was not "steep" enough.

I ended up getting the Harbor Freight offset wrenches, worked perfectly and the 9 mm is very nice to hold the shock while unscrewing the 18 mm. I could not get the 18 mm nut undone and my 18 mm deep well sockets were not deep enough. Harbor Freight to the rescue, I used the socket below, it's deeper as compared to my Craftsman standard 3/8" and impact 1/2". I was able to shove the wiring in it and use my electric impact wrench to get the nut loose. I ended up cutting the wire too long IMO.

Happy garage days ahead! When I get the new bag assembly, it's going to be minutes to replace it as I did not take the pinch bolt out to get the assembly out.