Rear of car very low after 4 days of non-use
 

Hi All

For the second time I've noticed that after being sat in the garage and not used for about 4 days the rear of my (new to me) car is very low on both sides. After the first time VCDS reported 403200 - Function Shut-Off Active > C10C8 00 [008] in Level Control which I cleared. However having driven the car tonight and then rescanned that fault code hasn't returned.

I've Googled for that code and seen various threads where it appears with other fault codes but nothing that matches my situation. Any thoughts on possible causes? Thanks!

Cheers - Graham

Not familiar with the D4, but would suspect the setup is very similar to the D3. With that being the case, I would initially rule out both rear air struts as being the problem (what are the chances of both developing a fault at the same time), and instead focus on the valve block as being the primary culprit. It could then either be a leak from the valve block or something internal. Spray on some soapy water, run the car and check for leaks. You could try spraying the struts as well, if it's easy to do.

Thanks for that! I'm glad to hear that checking for leaks is as easy as spraying on some soapy water :). The car will be going in to my Audi Indie soon for a few other jobs so this will be on the list. Right now I'm hoping to get an idea of the possible culprits so I can check if they will be covered by the warranty that came with the car. And also to get an idea of how easy it might be to narrow things down. Cheers!

Okay, just getting back to trying to get this sorted. My garage have done extensive leak testing but have found nothing, so looks like it will be trial end error part replacement if I want to get this fixed.

I'm going to do some tests over the next few weeks by leaving the car in different settings including jacking mode. In the meantime can anyone help me understand these observations and if they help pinpointing a faulty component:

Car is left for several days and the rear (both sides) drops right down (67cm from ground to top of wheelarch). I open the driver's door and I hear a hissing sound and the rear of the car rises to 74 cm. I start the engine and the car rises by about another 1 cm.

Despite the leak it seems that something is staying pressurised. Thanks for any help on this!

Assuming that the D4 air suspension works in a similar fashion to the D3, then there should be an accumulator (tank). It's a pressurised tank, and the system uses this where possible, instead of constantly relying on the compressor. The D3s also had a smaller tank attached to each of the rear suspension struts.

Regarding the hissing and the car rising, it is part of the 'wake-up signal'. I know it's not relevant to your car, but check out SSP292 in the D3 Tech Dump section, for an understanding of how the system works.

Thanks for all that Steamship! Pretty sure there is an accumulator as I've seen this mentioned on a different D4 suspension post. Good to know this is probably okay. I will take a look at that study guide - with a large pot of coffee :ROFL:.

The attached SSP below is specific to the D4 with complete layout of all pipes and components

Hope it helps.

Okay, leak now sorted. For anyone else with this my assumption that the rear of the car was dropping both sides evenly was VERY wrong and after advice to actually measure what was happening (I measured each side every hour for a day and part of the next day) I realised that the RHS was dropping whilst the LHS was static until it had to drop to keep even (there's a levelling mechanism apparently).

The whole repair procedure is a real pain though as the rear seats and parcel shelf have to be removed to get to the top of the strut. On removing the strut my garage found that the shock absorber had been leaking causing a bad seal with the strut and that seems to have been the root of the issue. They managed to source new aftermarket parts but even so this is not a cheap repair: parts were about £1,000 (I did NOT know a shock absorber could cost £600) and the procedure required a lot of labour to carefully remove and then reinstall the parcel shelf and seats.

All done now and completely stable after 48 hours.

Glad you got it sorted after some ingenious detective work.

Was somewhat surprised when you mentioned about the seats and parcel shelf removal, as the D3 ones don't require this amount of work to remove.