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I have posted this in the RS4 forum as well as its DRC related although my cars an RS5.
Had some rattles from the front drivers suspension and the passenger side rear so booked the car in. Have to say the service from Nottingham Audi was really good. I went out with a technician and at first the knocking was not apparent but thankfully after a few circuits of a short route it started with a vengeance!
Got the car back on Saturday and they had re pressurised the DRC system and applied 2 software updates, one to the DRC and one to the gearbox. Cant really notice the gearbox one but in Auto mode of the dynamic setting the rev blips on the down changes don't seem to be as aggressive. So far no knocking and the car feels very solid and like new!
My only query is that if the system has to be re pressurised then does that mean it is/has somehow lost pressure and if so wont it just happen again?
Mines a 2011 car btw.
I decided to enquire about RS4 Avants and have one for the day next Saturday but seeing my car being driven by someone else makes me reluctant to change although I could do with an estate as have just inherited new children!! Why does your car always look better when you see it being driven by someone else?

Hey Arsey, so I had a response back from my dealer this week also. Similar response from them below:

The repair for the knocking noise from the front shock absorbers was resolved by performing a software update to the wheel damping control unit. I was discovered that the knocking noise is caused by a quick reduction of oil pressure inside the DRC pressure valve, caused by the bump, this knock is transferred along the pipes and amplified through the shock absorber.

Low DRC fluid pressure can amplify the knock so a DRC recharge was carried out to remove any air in the system and ensure a correct fluid pressure of 20bar.

I suspect the software update has made a alteration to the function of the control valves in the shock absorbers to improve fluid flow rate in the DRC system to the central valves.

Having got the car back, I've hardly driven it, but I certainly didn't hear anything for the few trips I've done. Fingers crossed

For all the years there have been DRC problems this is the first official description I have ever seen as to what causes the famous knock. Is that the actual letter from your Audi dealer ? Hope that's it sorted buddy !!!!!!

Thanks for this info smudge - my car is booked into the dealer in a couple of weeks time for the knocking to be looked at and its great to have some 'solutions' from other owners should I get the inevitable 'they all do that' line.

Ill ensure I take info on as many potential fixes along!

Cheers!

Thanks for that smudge. Mine was really rattling but seems to have stopped although I still get a bit of a clonk on the right hand side when I go over bumps when cold. Bizarrely its only the drivers side!
Seems amazing that its 7 years ago when the original B7 letters and online pole went off to Audi and its still happening but on the flip side it is a very good system when its not knocking.

Alas the update has not worked, the knocking is back!

Got the car back again this morning and they have 1) Drained the oil from the DRC system 2) replaced it 3) Repressurised the system and left it overnight and rechecked in the morning.
Hopefully that will sort it.

Fingers crossed.

I took mine out for a drive around London this morning & despite the atrocious pot holes & bumps, all seemed to be fine. Looks like Jack Barclays have fixed mine. Hopefully yours is sorted too ARSEY4...

Updated from my 'issue'............

Its been back to the dealer.....air lock in the DRC from the factory........drained and vacuumed (for 40mins as apposed to the recommended 10mins according to the Master tech)

New DRC fluid....pressurized.........seems to be OK!

They also test drove against the 2 RS4's they have as pre-owned and according to the master tech they both had what Audi UK are still calling a 'quirk of the DRC on RS4's' and a lot nosier than mine was....

Well mines been fine up until last week when I did a 50 minute drive to Meadowhall. It was a slow journey with lots of bumpy roads and surprise surprise when I got there the DRC was knocking again. Whatever they are doing has worked to a degree as it no longer knocks on a journey when it used to but it seems to be heat and load related and all I can guess is that the system is failing when it gets up to a certain temperature. Anyway its booked in again so hopefully see what happens.
They told me it may be some air in the system and they also told me the cold clonk when it goes over a bump is normal! Funny that it only clonks on my front drivers side?!

Maybe it's both sides but seeing as you are sat on the drivers side you hear/feel it more.

Cold clunk is normal,if the pressure is ok I wouldn't worry!! some people won't notice this as their journey first thing might not involve bad roads

I hope that cold dunk term isnt an Audi excuse......

Not sure Audi R&D would sign any car off with loud noises coming from suspension - hot or cold...just cant see it happening!

Mine is going in next week or so for this and I'm not going to accept that is reasonable - they can take them off for me and I will fit a PSS9 kit like we did on the RS3 - it was amazing!

Mine is just under 6mths old and happy to reject the car over this as the noise is poop but I have every faith in Audi to fix it

i have been on with this for 1 year and everthing has been changed and i am sorry to tell you all but there is no fix and audi tech have classed this knocking as normal.
I got rid of the car as audi refuse to reject the car with this problem and it is affecting 2nd hand values as people ofload.

DRC is crap and that is why they will not be doing any more models with it.

Thing is, it's fine on most RS4 and was never an issue on C6 RS6. Not heard of any issues on C7 yet either.