A6 C6 rear suspension dropping

[PaulF2.5TDi]

I've had a look around here and elsewhere and it appears that (unlike the C5) this is not a common problem as I only found a couple of faults that were not the same as my issue.

Just recently, if the car is left for a couple of days, the passenger rear side drops to the stops from the 'Automatic' setting.
On starting the car, the green suspension light remains on for a short while until the car has risen a little and puts it out.
I have not tried any other setting yet (that's the next test when the car is going to be left idle a couple of days)

I have scanned it with VCDS - no fault codes, although as I think as soon as the ignition is switched on the pump starts.

I had a battery that was just starting to fail, which I have now replaced and coded a couple of days ago.
The only way I knew about the battery was if left for a few cold days the car would start normally, but the battery protection system had cut in.

I would have thought that if the level sensor was u/s, it would give a code or amber caution light.
Equally if the spring or pipes leaked causing it to drop, the car would not be in the position selected, so I would expect a code or fault light.

I have had a look with VCDS at what is going on but the labels are a bit lacking so I'm unsure of what many of the measurements are.
It appears that one of the blocks is the ride height as on reading is lower than the others and it seems to come up with the engine on.

I'm going to try and leave it on different settings and see if that helps, then trace the pipework with a fairy liquid filled brush looking for leaks.

Any pointers on where to look or what VCDS reading are worth looking into?

[Duggy72]

Try sending a message to bag piping Andy from the c5 section. He is an expert on these matters. Sorry I can't be of more help.

[motionpotion]

I have very similar issues with my 2006 A6 Allroad. Initially mine started out as dropping on the right hand side rear (drivers side rear) after a few days parked and only in automatic mode but it has now started to drop within an hour of stopping the car and on both passenger and drivers side on all of the height settings (automatic, dynamic, comfort, allroad) settings.

I also have no fault codes. But I do have a battery problem which I think is related to the compressor trying to run all the time to keep the air suspension inflated while stopped.

I would also like to know how to fix this - hopefully without having to buy new air suspension.

[PaulF2.5TDi]

Thanks Duggie - I probably will at some point as I'm not a million miles from him.

I saw your issue Motionpotion - the battery did not fix mine although it really turns over fast now!

I'll try and look over the next few weekends, but I suspect a valve in the solenoid block not sealing properly.
If this is the case I expect it will be a bugger to find.

If I find no leaks, I'll try some light oil through the solenoids - the environment my cars live in is not nice!

Do you have the problem at other settings?

[motionpotion]

@PaulF2.5TDi I swapped in new battery tonight and it's turning over faster but didn't fix anything with suspension.

Mine drops on back right drivers side at Dynamic, Automatic and Comfort settings. It does not drop at Allroad until about 2 days parked up and then it drops evenly on all corners.
I have not tried parking it up in Lift setting.

[PaulF2.5TDi]

An update on this - for what it's worth!

I haven't fixed it yet - but there are more clues.

The car seems to drop overnight - not slowly over time.
It can go a week without dropping, or (last week) drop whilst at work (dynamic).
It is only one corner that goes down.
There are no fault codes in VCDS.
The flashing green and yellow suspension lights may or may not come on. (I suspect if the yellow light is not on it hasn't dropped enough to trigger it)
The lights do not always go out once the car is back up - switching ignition off and starting again clears them.
It doesn't seem to matter what ride setting its on - although 'locking' it in Jack mode seems to stop it. (Although the drop in Dynamic may have been in jack mode too)
It appears to happen more often when it is cold (temps around freezing)
The suspension module had the wrong code when I bought the car last April (no tow-bar bit set) so I wonder if it has been changed already for this problem over the last winter by a previous owner.


This does not seem like a leak - more an intermittent module or sensor issue, but would this happen with the cars ignition off when parked?

[MarkTM]

For those without air suspension that's what's being talked about in this thread :)

[Arragonis]

For those without air suspension that's what their talking about in this thread :)

They're :p

[Crasher]

You have a leak Sir, a leak! Putting it in a high setting and it no longer dropping can suggest a bag hole but it not deflating in jacking mode could indicate a solenoid valve block (4F0 616 013) leak which will often not register a fault code as the individual valve elements (N150 in your case) do not have individual pressure monitoring.

[PaulF2.5TDi]

Thanks Crasher,

I suspect the valve block - but am trying to eliminate the cheaper options first!
I still haven't tried light oil through the pneumatic side of the solenoids yet.

I also wonder how the water is drained out after multiple compressor operations?

For info, the rear air spring is around £300 from Audi (not exact as I asked them for a price around the time when I started the thread) - not awful!
( I hadn't asked for a valve block price..……)


Out of interest, why would it not deflating in Jack mode indicate a valve block, and if intermittent why could it be an air spring?

[bagpipingandy]

Thanks Crasher,

I suspect the valve block - but am trying to eliminate the cheaper options first!
I still haven't tried light oil through the pneumatic side of the solenoids yet.

I also wonder how the water is drained out after multiple compressor operations?

For info, the rear air spring is around £300 from Audi (not exact as I asked them for a price around the time when I started the thread) - not awful!
( I hadn't asked for a valve block price..……)


Out of interest, why would it not deflating in Jack mode indicate a valve block, and if intermittent why could it be an air spring?

Hi Paul,

On the C5 its usually the airbag which causes the strange intermittent sinking as the airbags on the C5 only tend to leak when the car is at its lowest suspension setting. I would be suspecting the airbag at fault from your description. to check this park your car overnight at its lowest level and monitor it, then park it at its highest level, if it always sinks at one and not the other it is the airbag,

the valve block is not so likely, as you would need multiple valves to be stuck open. the valve bock has 6 valves, 1 for each of the 4 corners, 1 for the compressor and 1 for the storage tank, so if your rear left valve was stuck open the car would still not sink as at least one other valve would need to be opened and even then only the compressor valve would cause the car to lower. so to have the rear left and compressor valve opened is less likely. even if the valve body was cracked then it would sink all the time at any level.

that's a cheap price for the airbag?
the valve block is about £150

the system lets moisture out by venting every time the compressor stops, you hear a sharp Whoosh when the compressor stops this is the N111 valve venting pressure and moisture out the airline to the valve block.

the reason on the C5 for sinking only at low setting is the airbag rubber perishes at the lower fold on the airbag, and perished rubber when you fold it the cracks open and so air leaks, but lft the car to a higher setting the cracks physically move 25-50mm higher to the straighter part of the rubber and so the cracks close,

if it never sinks at low or high while in jack mode then its an electrical issue, could be valve block 10 pin connector of level sensor but I would hope to see a fault code for those,

do the parking at low and then high test over the next few nights, and let us know what you find

best regards

Andy

[Crasher]

The valve block is £290.99, the system drains from the pump body mounted suspension controller electronically operated drain valve, for which there is a £75.60 repair kit.

[PaulF2.5TDi]

Thanks guys,

It's in 'Jack' mode at the moment, on 'Lift' setting and has been up for a couple of days now.
I'll put it in 'Dynamic' this afternoon and lock it in 'Jack' mode and see where it goes.

The problem with this sort of fault is it takes an age to confirm the exact sequence of events, but with the cost of the parts I'm not just swapping bits without confirmation!

The C6 spring is separate to the damper - unlike the C5 and it looks like you can only buy the complete spring and not the bag.
As a result, leak checking it appears all but impossible.
(I haven't taken the bellows off yet to confirm)

AUDI A6 ALLROAD QUATTRO [A6AR] (EUROPE) 2007: REAR AXLE: 51110. AIR SPRING; SHOCK ABSORBERS; ANTI-ROLL BAR (http://www.partsbase.org/audi/audi-a6-allroad-quattro-a6ar-eu-2007-51110-air-spring-shock-absorbers-anti-roll-bar/)

From the above, looks like the spring repair kit is just for the bellows.

Interesting there is a repair kit for the drain valve - also the differing mod states.

[Crasher]

Yes, you need part number 4F0 616 001 J which is £333.62 inc.

[2fquick]

Hi I am also getting an intermittent drop on the right rear.
I will try leaving it in High & Low setting to see if there is any difference

Seems odd that 3 people have the right rear drop, no fronts or left rears?

PaulF2.5TDi, have you made any progress in finding the fault?

[PaulF2.5TDi]

Hi,

I keep meaning to write a piece with photos, but yes I replaced the spring following Andy's and Crashers input and all is now fine.

I got the spring from here - Audi A6 - C6 Allroad Suspension Air Spring Rear - Left or Right - Air Bag 04-11 | eBay (http://www.ebay.co.uk/itm/Audi-A6-C6-Allroad-Suspension-Air-Spring-Rear-Left-or-Right-Air-Bag-04-11-/231419685929?hash=item35e1b02c29:g:keEAAOSwg3FUisZ g)

It was not too difficult to do-

Put the car in lift, and then engage jacking mode on on the MMC

Jack the car by the chassis until the wheel is off the ground, rest on an axle stand or similar and remove the rear wheel.

Undo the two screws either side of the shock strut and pull the wheel arch liner out of the way.

Cut the tie wraps holding the spring air pipes to the body, and undo the pipe at the connector the air will hiss out

Undo the bolt under the arm holding the spring in place (it is a spline bolt, NOT torx or Allen - can't remember the size)

If you are replacing the spring, use a pin punch or similar bit of metal/bolt and loosen the spring in its seat with a big hammer.

I then screwed a wheel bolt into the hub and put a deep socket over it with a load of 1/2" extension bars.

I sat on the bars, pulling the hub down and removed the spring with a bit of jiggleage

Cleaned up the 'seat' and transferred the pipe

Sat on the spring to compress it and then sat on the extension bars and stuffed the spring into its seat - lining up the notch (really obvious and easy to do)

Replaced bolt in the bottom of the spring and got off the 1/2 extension bars then removed the wheel bolt from the hub

I then used a compressor and bed inflator (blue IIRC) to inflate the spring a bit

Then connect the air hose and ty-wrap it as it was previously

Refit the wheel arch cover and wheel then drop the car onto its wheels

Start the engine, release the jack mode and select dynamic.

There may be error lights flashing- depending how much you inflated the spring

Once all is in dynamic, turn off, then restart and select another mode
The lights went out and it rose much faster than it used to.

All is now good.

Less than two hours with stopping for beer :beerchug:

I decided did not need VCDS for this as the spring is dumb - it just inflates until the sensor says stop and Elsawin made no mention of it.

About two months later I has a suspension light (I can't remember the code but it was to with calibration) that I decided needed a calibration post spring change so did - there were differences that may, or may not have been there before.

I also found a wheel with low tyre pressure and inflated it……….. you decide what fixed the problem so whether you need VCDS for the change but I suspect the tyre inflation was the problem!

[bagpipingandy]

sounds like another airbag, rear airbags go 1st on the C6 for some reason, on the C5 its the fronts

best regards

Andy

[PaulF2.5TDi]

You and Crasher were spot on with my one Andy cheers for the help.

[2fquick]

Thanks guys
I'll get the parts ordered & swap the airbags out

Recommend to replace both at the same time or wait for the left hand side to fail before changing?

[PaulF2.5TDi]

I just did the one - FWIW