2020 B9.5 RS4 Vorsprung knocking noise DRC recharge

[spidmack]

Hi folks,

For a while I noticed a knocking noise from the rear of my 2020 B9.5 RS4

My local dealer currently have the car & have noticed a 1 bar difference.

They are going to recharge & test again.

I’ve seen a few posts of Audi owners reporting DRC issues however not any on the B9 or B9.5 RS4 & wondered if anyone else had this issue?

On another noisy note. My brakes have the common issue of squeaking while slowing down at town driving speeds.

If anyone has any information especially on the DRC knocking noise I’d be interested to hear

Thanks folks


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[RS4John]

There have been reports on here of B9 DRC issues previously - usually knocking. IIRC it usually ends up with the damper unit being replaced.

Same for squeaky front disc pads - the pads will have a glazed surface. You can do a couple of hard stops from 60 mph and that should fix it. I put EBC Redstuffs in my B9, and now the same with the F3 RSQ3 (its actually the same pad). No squeaks, little dust and no disc wear.

[spidmack]

There have been reports on here of B9 DRC issues previously - usually knocking. IIRC it usually ends up with the damper unit being replaced.

Same for squeaky front disc pads - the pads will have a glazed surface. You can do a couple of hard stops from 60 mph and that should fix it. I put EBC Redstuffs in my B9, and now the same with the F3 RSQ3 (its actually the same pad). No squeaks, little dust and no disc wear.

Many thanks John. I’m waiting how they get on after the re-charge. It’s only a year old so still in warranty.
I’ve tried the hard stops but it never fixed the issue. My dealer suggested a clean of front & back discs but as I’m over 6 months old I’d be around £350 so I declined. I should have got in touch earlier as it’s done this since 2 or 3 months old. I suspect even if I paid for the cleaning it would just come back in a few months time . Your idea of the EBC Redstuffs is interesting. I might try those.
Thanks for your help


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[jamiemcd]

I've had a rear damper replaced on my B9 (under warranty luckily).

[Markp]

1 bar down isn't much and can happen with careless disconnection of the charging hoses.
From memory the system is charged to 20 bar to test for leaks, then dropped to 16 bar. Which suggests yours is 15. It should not be knocking at that.
Don't ask me how I know.....
The squeaking is normal. Been there on all my RS's. Best to learn to live with it.

PS DRC knock normally comes not from the dampers (they are often the source of leaks) but from the accumulator / valves that sit under the floor at the back of the car. Classic symptoms are that the noise is worse in Comfort, at low speeds over rough road, manholes etc, and when heading downhill for some reason. Remove the rear boot floor to hear it more clearly. I have had ongoing problems with mine finally traced down to two slow leaking dampers - replacing these and both valves (this is important as low pressure in the system can damage them) has fixed the issue finally.
It is a brilliant system but under very high pressure with a relatively small volume of oil / fluid and even the slightest leak will lead to knocking over 5-10k miles.

[spidmack]

Thanks folks for your help / updates. Here's where they are. The garage tried a recharge however it made no difference.
I gather they then attached microphone(s) to different parts of the car and now think the cause may be the one or both of the two accumulators behind the bumpers.
So they plan to replace them both.

This would concur with Mark's post re slow driving around town and matches what I was experiencing. For example I didn't hear the issue on on the motorway just around town.

They are on a a 10 day back order from Germany.

Since they are not certain where the issue is from they have advised to not drive the car and are currently sourcing me a loan car.
In addition they noticed an issue in the rear exhaust silencer. Apparently there was an an issue with the valves and water in the silencer so have also ordered this.

Just as well my car is in warranty.

Looking at the timescale it seem unlikely I will get it back before Christmas.

[Markp]

Oddly my car had just had a new silencer for duff valve (n/s) too.

[spidmack]

Oddly my car had just had a new silencer for duff valve (n/s) too.

Ah thats's a co-incidence. Mine is a 9.5 B9 RS4. I took delivery Oct 2020.

Did you notice the issue? If so what were the symptoms?

On a side note. I'm in a A6 Sline Avant. It's nice but of course not as nice as my RS4. It's also not as smooth over bumps around town

I cant fault my dealers service. They have been good to deal with.

[Markp]

Oddly my car had just had a new silencer for duff valve (n/s) too.

Ah thats's a co-incidence. Mine is a 9.5 B9 RS4. I took delivery Oct 2020.

Did you notice the issue? If so what were the symptoms?

On a side note. I'm in a A6 Sline Avant. It's nice but of course not as nice as my RS4. It's also not as smooth over bumps around town

I cant fault my dealers service. They have been good to deal with.

It was flicking between dynamic and comfort (sound) on that side every few secs. Flap had a mind of its own.

[spidmack]

Oddly my car had just had a new silencer for duff valve (n/s) too.

Ah thats's a co-incidence. Mine is a 9.5 B9 RS4. I took delivery Oct 2020.

Did you notice the issue? If so what were the symptoms?

On a side note. I'm in a A6 Sline Avant. It's nice but of course not as nice as my RS4. It's also not as smooth over bumps around town

I cant fault my dealers service. They have been good to deal with.

It was flicking between dynamic and comfort (sound) on that side every few secs. Flap had a mind of its own.

The tech mentioned something about the valve / flap. Maybe it’s the same issue. Is the flap just on one of the two tail pipes?


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[Markp]

Yes.

[spidmack]

So here’s an update. The accumulators were replaced however this hasn’t fixed the issue.

They have a shock absorber (s) on order & will try swapping it (them)

Hopefully this fixes the issue. That’s 3 & a bit weeks my car has been at the garage now. Delays caused by parts taking time to source & the festive break haven’t helped. I do have a loan car albeit not as nice as my RS4


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[spidmack]

Here another update -

My Oct 2020 B9.5 RS4 Vorsprung has been at the garage for 30days.

The DRC system was initially thought to be the cause. The system was re-pressurised & didn’t fix it.

The two accumulators were replaced & didn’t fix the issue.

The drivers side rear damper was replaced & didn’t fix the issue.

The passengers side rear damper was replaced & didn’t fix the issue.

A secondary issue with the exhaust was noticed. Parts were replaced.

I understand the noise is a bit better but there is still an issue. So the garage are still trying to diagnose the cause of the problem.

It’s been a fantastic car apart from this issue.

Dare I say it. I’m wondering if they will be able to fix the problem & if so how much longer it could take.


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[spidmack]

Hi Mark, Did your DRC / suspension noise get fixed totally?

The guy's at my dealer have been trying to fix it.

They have replaced the two accumulators and the two rear dampers + a section of the exhaust. I'm not sure if the valves have also been replaced.

Apparently it's much improved but not gone totally.

They wanted to do a comparison to another RS4 but none of the ones they have, have DRC. Their suspicion is this might just be a feature of the DRC suspension. In that you get a knocking noise from the system at low speeds?

I'm going up tomorrow to head out on a test drive, to see if it's acceptable.

Thanks for your help

1 bar down isn't much and can happen with careless disconnection of the charging hoses.
From memory the system is charged to 20 bar to test for leaks, then dropped to 16 bar. Which suggests yours is 15. It should not be knocking at that.
Don't ask me how I know.....
The squeaking is normal. Been there on all my RS's. Best to learn to live with it.

PS DRC knock normally comes not from the dampers (they are often the source of leaks) but from the accumulator / valves that sit under the floor at the back of the car. Classic symptoms are that the noise is worse in Comfort, at low speeds over rough road, manholes etc, and when heading downhill for some reason. Remove the rear boot floor to hear it more clearly. I have had ongoing problems with mine finally traced down to two slow leaking dampers - replacing these and both valves (this is important as low pressure in the system can damage them) has fixed the issue finally.
It is a brilliant system but under very high pressure with a relatively small volume of oil / fluid and even the slightest leak will lead to knocking over 5-10k miles.

[Markp]

Yes. All fixed.