Free guide · 2005–2008 · BNS 4.2 FSI · 420 PS
Audi RS 4 B7: what to check before you buy
What this car is, and the six questions that decide whether the one you are looking at is a good buy.
In this guide · 6 chapters
Who built it, and what they built
A naturally aspirated V8 that runs to 8,250 rpm, in a car that looks like an A4 in a car park. The BNS: 4,163 cc, direct injection, 420 PS at 7,800 rpm, built from 2005 to 2008. Six-speed manual — the only gearbox it was offered with. Saloon, Avant and cabriolet.
What is unusual about it, specifically
Everything about how it makes its power. 420 PS from 4.2 litres without a turbocharger means it has to rev, and it does: the limiter is at 8,250, which is motorcycle territory for a family saloon.
And there was no automatic. Not as an option, not late in the run. If you are looking at an automatic B7 with a V8, you are looking at an S4, which is a different car with a different engine and a different set of problems.
It is the exact opposite of how fast cars are made now — no turbos, no paddles, no software making up the difference.
One piece of genuinely good news, before the rest
The chain story you have heard is mostly about another engine. The Audi 4.2 has a reputation for rear timing-chain work, and the best-known part of it belongs to the S4 4.2 40v, not to this BNS. Audi gave the high-revving RS 4 engine its own sleeve-type chains, for "reduced wear and higher stress resistance at high engine speeds", and we have found no documented failure pattern for it. Chains exist and tensioners wear, so it is not a subject to ignore — but a forum thread about an S4 should not set the price of an RS 4.
And one warning that shapes this whole guide
Two of the expensive items on this car are known in advance, not bad luck. Carbon on the inlet valves comes with direct injection. The DRC dampers are a known leak — known well enough that, in the US, Audi offered owners improved dampers free of charge. That means a well-kept RS 4 has invoices for them, and a cheap one has them still to come. The difference between those two cars is far larger than the difference in their adverts.
How the figures in this guide work
There are no prices in here, and that is deliberate. A workshop rate differs by a factor of two or three between countries, so a figure we cannot verify for you is worse than no figure. What does not move is how much work a job is — that follows from what has to come off the car.
So every item says whether it is an hour or two, half a day, a day, two or three days, or a week or more in the workshop, and whether the money sits in the part or in reaching it. Ask any garage one question — what is your hourly rate? — and every item becomes your own number.
The six questions that decide whether this car is a good buy
If you read nothing else, read these. Every one can be asked on the telephone, before you spend a day travelling.
1 · When were the inlet valves last blasted clean, and is there an invoice?
Direct injection means petrol never washes the valves. This job comes round, and "never" on a high-mileage car is a bill you are buying.
2 · Are any of the DRC dampers wet with oil?
Ask them to look, or look yourself. This is the item that can turn from one damper into the whole set, and the reason is in the buying guide.
3 · Has it had coil packs, and has it ever run with a misfire?
Coils are cheap. A misfire left alone is not, because unburnt fuel can take a catalyst with it.
4 · Does it smoke blue, especially after pottering about?
On this engine blue smoke has a known cause, and it says something about how the car has been used. What it points at is in the buying guide.
5 · How does the clutch feel, and has it been replaced?
There is only one gearbox on this car, so there is only one answer that matters.
6 · Has it been tracked, and does the service history have names on it?
Neither disqualifies a car. Both change what you inspect.
Which years, which specification
2005 to 2008, and that is the whole run. 4.2 FSI, 420 PS, six-speed manual. There is no facelift to learn and no engine change halfway through.
Three bodies. Saloon, Avant and cabriolet, all with the same engine and the same gearbox. The mechanical guide below applies to all three. The cabriolet carries more weight and the Avant is the one people remember. Mechanically, neither changes what you check — but the cabriolet adds an electro-hydraulic hood, so run it through a full open-and-close cycle at the viewing.
What to look at instead of years. How it has been used, and what has already been done. Because the run is short and unchanged, the spread between a good RS 4 and a bad one is entirely about history — not about picking the right model year.
One specification note. DRC was standard. Some owners have converted from DRC to conventional coilovers. That is not automatically wrong, but it is a different car to drive and a different car to value, and it should be declared rather than discovered.
What it is worth
Not in money — see above — but in the only currency that matters when you are standing next to one.
An RS 4 is priced as a fast Audi and maintained as a high-revving V8. The two costs that define it — valve cleaning and DRC — are both invisible in a photograph and both obvious in a folder.
So the value of a specific car is not what it is listed at. It is:
- when the inlet valves were last cleaned, and
- what all four dampers look and feel like, and
- whether anyone has been chasing a misfire.
A car with a recent valve service, dry dampers and a documented history is worth substantially more than its advert suggests. A car at two-thirds the price with none of those is not two-thirds of the car — it is the same car with the bills still in front of it.
What it is actually like to own one
Quick in a way that has become rare, and quiet about it until you commit.
Below 4,000 rpm it is an A4 with a good engine. Above it, the V8 does the thing that turbocharged cars cannot: it keeps going, and it keeps getting louder and more urgent, all the way to a limiter most modern engines never approach. The six-speed manual is part of the point.
What you do not get is a car you can drive gently and ignore. Pottering is actively bad for it — oil gathers in the inlet, carbon builds on the valves, and the car that never gets revved is the car that needs the inlet off soonest.
The honest summary: the RS 4 rewards being used properly and punishes being kept nicely. That is an unusual thing to say about a twenty-year-old fast car, and on this one it is the single most useful sentence in the guide.
The buying guide — €24
Everything above is what the car is. This is what you check.
Five faults that belong to this car, taken apart one by one, with how much work each repair is and how to tell which of them you are looking at. Eleven things that are simply twenty years old, every one with how much work it is, what tells you about it at a viewing, and whether it has to be done now, within a year or two, or not at all. Why the body is the short chapter on this car, and what ride height and wheels tell you instead. Why gentle use is worse than hard use on this engine, which two costs you can know about in advance, and what Audi itself did about the DRC dampers in the US. The viewing in eight steps, including the two moments that come only once. The sentences you say to the seller, and how to build an offer out of what you found.
And a card you print and take with you — twenty lines, in the order you do them. That comes as a separate file, because nobody wants to print a whole guide to take a few pages to a car park.
This is what one of the eleven looks like
10 · Exhaust, mountings and air conditioning
Half a day each · ordinary Twenty years underneath a car, and two decades of seals.
When they announce themselves.
And this is how the card reads
- Standing, before it is started
- Cold start
- On the move
- Data and paperwork
What €24 buys, put next to what it saves
The DRC dampers are the one to price: a single leaking unit can become the whole set — a day in the workshop, with the parts making up the majority. It is also one you can check at a viewing, in thirty seconds, for nothing. The guide is €24. It will not stop any of that from being needed — but it does tell you which of them you are looking at before you agree a price, and that is the whole of the difference between paying for a car and paying for someone else's postponed maintenance.
Why there are no prices in it
Because a price we cannot verify is worse than no price, and because a price would be wrong for most of the people reading this anyway. Workshop rates across Europe differ widely, and so do parts prices. A quote from a specialist in one country tells you nothing in another.
What does not change is how much work a job is — that follows from what has to come off the car. So every point in the guide says whether it is an hour or two, half a day, a day, two or three days, or a week or more in the workshop, with a labour figure where a source gives one. And it says whether the money sits in the part or in getting to it, which is what lets you tell a fair quote from a bad one.
If you want a figure, ask any workshop one question — what is your hourly rate? — and every effort level in the guide becomes your own number, in your own currency. One question, and the answer is actually true for you.
How this guide was put together
Because you should know before you pay for it.
- Every fault and symptom comes from a source the guide names, the manufacturer's own documents first. The effort levels are our assessment, unless a source gives the hours.
- The guide says plainly that the best-known timing-chain reputation of the Audi 4.2 belongs to the S4 and not to this engine — and it still covers the chains, because chains exist and tensioners wear.
- The effort of every job is counted item by item and checked against the list before every edition.
- It says as plainly what you can leave alone as what you have to do. Two of the eleven age points start from leave it.
Leave your email address at the checkout and both files arrive straight away: one guide and one card, as two pdfs. No subscription, no account.
The full guide · €24
16-page guide, A4 and phone · 2-page inspection card · instant PDF · VAT included
Have every car inspected before you buy by someone who knows this engine. This is general information about the model and not advice about a specific car.