Free guide · 2006–2010 · N54B30 · 306 PS
BMW 335i N54: 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 straight six with two turbochargers, in a mid-sized BMW, from 2006. The N54B30: 2,979 cc, 306 PS, in the 335i from 2006 to 2010. Six-speed manual or the ZF six-speed automatic; late coupes and convertibles could also have the seven-speed dual-clutch.
What is unusual about it, specifically
Not that it is turbocharged — everything is now. What is unusual is how it was turbocharged, and what BMW was willing to spend to do it.
Two turbos on six cylinders, direct injection with piezo injectors, and a fuel system running at pressures that the industry was still learning about. The result is an engine that makes 306 PS as delivered and a great deal more with software, which is why so many of them have had software.
That is also the whole problem. This is a complicated engine sold in an ordinary car, at a price that now puts it within reach of people who budget like ordinary-car owners.
Two pieces of genuinely good news, before the rest
In the United States, most of the expensive faults were covered by the factory, for a long time. BMW of North America extended the warranty on the high-pressure fuel pump to ten years or 120,000 miles, gave the last cars the same on the injectors, and covered the turbocharger wastegates for eight years or 82,000 miles. Those covers applied only to cars registered in the US, and they have expired — but a car whose pump and injectors were replaced under them is a car in which two well-documented failures have already been paid for by somebody else. Outside the US, ask what was replaced and when, not under which warranty.
And the parts got better as they went. The injectors exist in several revisions, and BMW's own bulletins say where the improved part begins. You are not looking for a car that has never had injectors; you are looking for one that has the late ones.
And one warning that shapes this whole guide
This is not a car where a clean fault memory proves much. The fuel-system faults normally do store codes — but a code can be cleared before a viewing, and BMW notes that a pump fault may show only under load. The most expensive item announces itself in a sound. A seller who says "no faults" has told you that the memory was read, or cleared, and nothing more.
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 · Has the high-pressure fuel pump been replaced, and do you have the invoice?
On US cars it was covered for ten years or 120,000 miles; elsewhere, the invoice is what counts. A car with that paperwork has had one of its well-documented failures dealt with.
2 · What index are the injectors?
There are several revisions, and BMW draws a line between the early ones and the improved ones. The number is on the part and a specialist can read it. This is the sharpest question in the whole guide, and most sellers will not know the answer — which is itself useful.
3 · Does it rattle or clank when you lift off?
Wastegate rattle. BMW itself separates a rattle it calls normal from the one that is a fault, and the fix depends on when the car was built: on some it was software, on others one or both turbochargers. It is also the expensive fault you can find with your ears — how, and what to listen for, is in the buying guide.
4 · Has the electric water pump been replaced, and when?
It stops without warning and the car overheats without building up to it. A date is an answer; "not that I know of" is also an answer.
5 · Has it been remapped, and is it still?
Software is not automatically bad, but it changes what the fuel system and the turbos have been asked to do. A seller who says no while the car has a flashed DME is the problem, not the tune.
6 · Will you let a specialist read the live data?
On this engine the fault memory is not the whole evidence; the live data is. If the answer is no, the viewing is over before it starts.
Which years, which specification
2006 to 2010 — the N54 car. Two turbochargers, 306 PS. This is the engine this guide is about.
What came after. BMW replaced the N54 with the N55, a single turbocharger with twin-scroll. Same badge on the boot, different engine underneath, different set of problems. If you are reading a forum thread, check which of the two it is about before you let it worry you.
Early versus late. Wastegate rattle is described as becoming more common with mileage and being seen more on early cars. In the US, the last cars also got the extended injector warranty. Neither is a rule you can buy on, but both tilt the odds.
Gearbox. Six-speed manual or the ZF six-speed automatic; the seven-speed dual-clutch appears on late coupes and convertibles. BMW's coupe data sheet valid from March 2009 lists it, while its September 2009 data sheet for the saloon lists only the manual and the automatic — check the individual car rather than the year.
Body. Saloon, touring, coupe and convertible all took this engine. The mechanical guide below applies to all of them.
What it is worth
Not in money — see above — but in the only currency that matters when you are standing next to one.
A 335i is priced as a used 3 Series and repaired as a twin-turbo. The purchase price is no longer the largest number in this transaction. A pair of turbochargers, a fuel pump and a set of injectors can each cost a meaningful fraction of what the car is advertised for.
So the value of a specific car is not what it is listed at. It is:
- what the paperwork says about the pump and the injectors, and
- what it sounds like from cold and on the overrun, and
- whether anyone will let you read the live data.
A car with a documented pump replacement, late-index injectors, a recent water pump and no rattle 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
Fast in a way that still surprises, and demanding in a way that catches people out.
The engine is the point. It is flexible, it is quiet until it is not, and it responds to software like almost nothing else of its era — which is why the aftermarket around it is enormous. The car around it is an ordinary, very good 3 Series.
What you do not get is the running cost of an ordinary 3 Series. This is an engine with two turbochargers, a high-pressure fuel system and a water pump that fails without warning, in a car whose purchase price says none of that.
The honest summary: the 335i is one of the cheapest ways to own something genuinely quick, and one of the more expensive ways to keep owning it. The owners who enjoy them are the ones who budgeted for the engine rather than for the badge.
The buying guide — €24
Everything above is what the car is. This is what you check.
Six 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 fifteen 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 modification history tells you instead. Why a clean fault memory proves little on this engine, and which two numbers in the live data decide the purchase. 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-three 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 · Brakes, bushes and tyres
Half a day each · ordinary Fifteen years of a quick car. Read tyre date codes rather than tread.
When they announce themselves.
And this is how the card reads
- Cold start, before anything else
- Standing
- On the move
- Data, before you agree anything
What €24 buys, put next to what it saves
The biggest job on the list is the wastegate rattle when it means one or both turbochargers — a day or more, with the parts making up almost all of it. It is also the one you can find with your ears, for nothing, at the viewing. 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 this is a complicated engine sold in an ordinary car — one of the cheapest ways to own something genuinely quick, and one of the more expensive ways to keep owning it.
- 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
17-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.