The B7 RS4 a buyers guide to common faults.

The B7 Audi Rs4 came out late 2005-early 2006 depending on where you were in the world. The 4.2 Litre Naturally-Aspirated V8 was designed to deliver 414bhp and 420nm, with a stratospheric redline of 8250rpm. The engine was fantastic being used in Audi’s first supercar the R8 with a few tweaks and a lightened flywheel. Despite the characterful power-plant being revered by Jeremy Clarkson, long term ownership and running uncovered a few teething problems.

The Brakes

The B7 came with massive 8 piston callipers stolen from the C5 Audi Rs6 and first generation Lamborghini Gallardo. They were paired with 365x34mm front brake discs and provided great stopping power. The Brembo discs proved to be the weak point however, with the drilled surface often filling with brake dust and failing to dissipate the heat. You’re then met with an unpleasant vibration through the steering-wheel and brake peddle. The main cure for this was to have your discs skimmed or opt for aftermarket replacements , being floating bells neither are particularly cheap. Skimming will cost around £150 however Reyland Racing offer replacement discs for around £350. These are slotted are not prone to warping.

Carbon (the swear word for B7 owners)

So you may have noticed I wrote what the power figures were supposed to be instead of the actual. Our friend carbon has a little involvement for that being the case. Most B7 and B8s for that matter,never made their quoted figures and over time the ports would be coated in carbon deposits. Every 40,000 miles or so the B7 requires the removal of its inlet manifold and all 8 ports manually cleaning (none of that cheap hydrogen crap). The cost is anywhere around £500 upwards as it’s a timely process, with Walnut shells used to “blast” the hardened carbon deposits away. I’ve seen B7 RS4’s run as low as 330bhp at the flywheel a solid 84bhp down on standard figures. A healthy example in stock form would maybe run 390-400bhp.


Audi pioneered Dynamic Ride Control (DRC) I believe in the C5 RS6 platform, a great setup when it’s working. Sadly this wasn’t often. The B7 and later B8 RS4’s are still plagued with reliability issues of the system. My first B7 had 4 sets of DRC before my ownership and it was starting to fail again. I opted for Bilstein B14 upgrades, which stiffened the car and transformed the handling overall. The driving dynamics alter a little with the chassis feeling more rear-biased and firm but for the money you can’t really complain. I think I was quoted £250 a corner for a DRC strut back then before labour and re-pressure. The £815 I paid for the Bilsteins and a few hours on my drive saved me a fortune and arguably improved the handling too.

Auxiliary radiators and Oil Coolers

The B7 RS4 in saloon guise was also sold in the USA (Audi don’t do that often), therefore it has some additional cooling to compensate. Beneath each headlight and behind the honeycomb grills there’s an Auxiliary radiator. The UK market only needs one but these are prone to leaks. However the good news is they are reversible RH-LH etc. Most remove the drivers side radiator and fit a cold-air intake kit when opting to remap the vehicle. The Oil Cooler sits at the bottom of the centre grill, with connections and pipes corroding until failure. This is easy to spot if you stick a torch through your front grill or you find oil on your under-tray. My first RS4 had a Forge upgraded unit, positioned higher in the grill it lowered temperatures by several degrees especially when driven hard. The forge unit sounds expensive at £500 however this is similar to replacing the standard part, if yours is perished i encourage an upgrade.

Inlet manifold flaps

So we’ve discussed venturing beneath the Inlet manifold to remove carbon however while you’re there it’s worth investigating the intake-flaps as well. My First B7 managed to nearly ingest one (sadly this isn’t a rare case). There is a shaft per bank and the “flaps” are held in place by two screws each. These unfortunately are known to come away and go through the engine causing heavy damage. My car fortunately was very lucky. It’s possible to leave the shaft in place and remove the intake-flaps, this can help confuse the ECU and avoid error lights. A remap is best after removal as it alters cold-starts and they sound a little rough. James at P&G automotive charged me £200 for this work as at the time I needed an oil feed pipe replacing at £100. With a carbon clean all at once I think my bill was £800.

Exhaust valves

The standard system has valves just before the exhaust tips. These are operated by a vacuum system hidden up in the rear bumper, however these are known to corrode and stick in one position. This is common on standard exhausts , the valves are designed to open with “Sports” mode engaged. You can delete this by fitting a non-valved exhaust system and blocking off the vacuum lines with small screws and cable ties (you’re welcome). A little tip on exhaust upgrades whilst i’m here , a “resonated” exhaust will have boxes in the centre section. These lower the volume of the system and prevent drone. “Non-resonated” systems tend to be effectively straight pipes all the way to the back-boxes. These are both louder and tend to drone at motorway speeds so maybe opt for valves.

Aluminium oxidisation

The RS4 has mirror mounts fitted made of aluminium you will commonly see these looking white and powdery. This is aluminium oxidation whilst you can have these powder coated it may be as well to just replace them as mirror removal is never the easiest thing on these cars. The going rate for a pair for mirrors is circa £400 upwards so you’ll want to be very careful removing them. The wings may blister as well , any good body shop will be able to rectify this but chances are you’ll end up having a full front end spray to colour-match.


Most Quattro drive-train cars are very sensitive when it comes to tracking, so if you’ve given it a whack with a pothole you’re best off having alignment checked asap. The B7 is more than happy to toe-in and kill your tyres very quickly. Again due to Quattro you may find the car tramlines depending on the tyres you’re using. I’ve heard a lot of reports of Pirelli’s being bad for this , most prefer the Michelin Pilot Sports.

Seat bolsters don’t always inflate correctly with sport mode. If you have a car with the sculpted buckets you may need to delve into the cars menu and turn this feature on. If you retrofit bucket seats you will need VCDS(VAGCOM) to program these in.

Check oil consumption a little every 1500 miles or so is pretty common, however if you’re encroaching on a litre every 1000 miles or less you may need to have the PCV replaced. This is a good maintenance item to replace during a carbon clean and fresh oil afterwards doesn’t hurt. Hope this helps any prospective buyers out there. I loved both of my B7s i won’t lie and say they’ll appreciate but they’re cheap manual V8 FUN.

Published by Sam Busby

a big nosed bearded idiot who likes to write about cars. Lucky enough to have owned a few quick ones too.

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