Leaderboard

I thought I'd reply to this as apart from being hopefully amusing it might help someone with a similar air suspension problem. Although it's about my 'forever car' I think one Audi air suspension strut and compressor system is much the same as another. A few years ago my 2005 D3 SWB W12 at 70,000miles started to sag at the front when left overnight. The compressor would restore the height and the orange and green lights would go off. But the tiny leak got worse and the compressor sometimes needed two goes at it, presumably because the thermal protection switch would cut in after much noisy pumping. Lots of air was lost from the system when the clever car tried to keep itself level by transferring air from the high pressured accumulator to the lower pressure leaky strut (see Audi SSP 292, P31). If overworked, the compressor or its relay will eventually fail. To locate the leaky strut, I put it in ‘jack mode’ to prevent level equalisation. Next day only the front driver’s side had bottomed out. I removed the under bonnet trim to expose the strut's upper mounting, slid the large dust cap back along the black wire, and did the same with the smaller dust cap underneath it. With jack mode off to restore pressure in the strut, I sprayed soapy water around the strut and poured about 15mls into the top of the mounting, not filling it above where the black wire goes in. No sign of leak from the strut air bag behind the wheel but foam appeared on top of the strut mounting. Diagnosis – the tiny top ‘O’ ring has failed, impossible to replace without major work and the garage rejoicing in a big bill for a new strut. I suspect this is the most common failure rather than the larger bottom ‘O’ ring or the tough air bag itself. I replaced the foam with about 20 mls of clear water. With a magnifying glass I saw a tiny stream of bubbles appearing from below the 18mm locking nut. So I put jack mode back on and waited a couple of days till the bubbles stopped when the pressureless strut had bottomed out. Then I sucked out the water and left it to dry thoroughly. Then I injected a layer of some tough ‘CT1’ sealant. After a day to harden, I added another layer….then another. Then, jack mode off to restore pressure in the strut. Sadly, it didn’t completely cure the leak, but it took around three days to sink rather than just overnight. But a little later the WABCO compressor finally failed, rattling away uselessly. Although access is via the wheel arch for most A8 cars, it is impossible for the W12. The front bumper has to expensively come off. So I bounced it along to my capable indy to do this and the compressor, reconditioned with my repair kit from ‘bagpiping andy’, is now silent. I could live with the leaky strut, remembering to put a bespoke 30cm x 12 x 6 wooden block under the jacking point with ‘jack mode’ on if unused for a few days. It’s important to leave the car in ‘jack mode’ so the compressor doesn’t have to replenish the whole system every time the car is used. Amazingly, a few weeks ago (at 76000 miles) I noticed the car no longer sank onto the block, even after well over a week. Somehow the amazing CT1 sealant (incidentally good for repairing trainer soles!) seems to have almost sealed this top end leak! I hope this story helps someone with a similar problem as I don’t believe I’m the only one with O ring failure which a garage would probably resolve with a new strut and a hefty four figure bill.

Just joined hoping someone would like to buy my wifes cherished dark blue A4 Cabriolet. 2 lady owners, 54000 miles, FSH and always garaged. She is looking for around £3000, having been offered £2400 by an unpleasant dealer who test drove it.thanks Bob

Looks fantastic, sounds like you've got a good plan to get it recommissioned. Slow starting could be worn out glow plugs or injector issue. Any blue smoke on start up could be failed injector seals. Please keep us posted on how you get on

You'd have thought so from the point of view of a practical mechanic, but the "master technicians" that Audi employ can only plug in their computers and read the screens, and if the computer says "no" you are out of luck yet still face a large bill.

The sagging must be caused by either a leak or a problem with the control system. The history of the problem is important. You said that it 'only seems to be when sitting a long time'. If it was the control system, the sagging would be present immediately, I think. If the level is OK for several hours, and then gradually sags, that is suggestive of a small leak gradually reducing the pressure in the strut. Have a thorough read of my post above and ask your expensive mechanics specifically if they have sprayed the strut bags with Fairy Liquid water (makes lots of giveaway bubbles) and also done the same as I did at the top of the strut housing to check the top O ring. It only takes a few minutes to do, and should have been the first thing they did.

I'm signing out of this forum but I thought you might like to learn that Audi in America advocate a long-soak method of oil flushing before oil change to try to solve this very common problem. It sounds very severe to me - 45 minutes at 3000 rpm after adding the substance - so I'd have reservations. But you can't buy it retail anyway, only through Audi dealers.

Interesting John, and fix. Just been listening to someone on YouTube with a Q7. They had sagging suspension overnight and replaced airbag suspension up front and the fault continued. According to them this was traced to insufficient tyre inflation. Now this got me thinking, hold on, this is a Q7, TMPS has been in place since 2012, so surely a incorrectly inflated tyre would have flagged an issue? Apparently there was an update to the story and it was in fact one of the self levelling sensors that was corroded. Would be worth checking them out that there’s no corrosion or damage before condemning the airbag.

Definitely could be a leaking airbag. I'd recommend a diagnostic check to see if any fault codes flag up

Apologies for the gripe, but the forum has recently suffered from a spate of what can be termed ‘Post and Run’ new members, who seem to think it’s perfectly acceptable to post a plea for help, and simply not return to view the help given. In a more diluted form, help is offered, but is very rarely acknowledged even via. a simple press of the Like button, leave alone a posted Thank You. The last part of the gripe is that we frequently have to ask for additional information, and this extra detail often never materialises. Please remember, everyone who posts replies do so without payment, but it certainly does cost them in time - in terms of the Moderators and Admin back up - a lot of time. So a special plea to all on here who post needing help:- please be respectful enough to acknowledge any help given, rather than simply accept it as a no-cost, no time of yours, free advice service. It’s wearing thin folks, so if you want to retain this service, please respect and acknowledge its benefits. Thank you all for reading this, and above all, agreeing to adhere to the respect that is needed to be shown. Kind regards, On behalf of the Moderators. Please note:- This request is to all members, not just new ones. p.s. Please avoid using non specific locations such as U.K., England etc. etc.

Never found why this is the case. Replaced everything and still get hot as if they are dragging. New calipers,discs,pads and wheel bearings. Gave up to be honest