# BMW Z4 M E85 / E86

> The free buying guide from Last Real Engines, updated 2026-10-13. Web version: https://lastrealengines.com/z4m-e85-e86/free-guide/ · full guide: https://lastrealengines.com/z4m-e85-e86/
## The story

*What this car is, and the six questions that decide whether the one you are looking at is a good buy*


## 1 · Who built it, and what they built

The Z4 was BMW's two-seater for people who wanted a roadster rather than a race car. Every one was built in
Spartanburg, South Carolina. In 2006 the M division took it and installed the engine
from the M3 E46 — and then changed almost everything around that engine, so that the rest of the car could keep up with it.

There were two bodies. The **Z4 M Roadster**, the E85, with a fully automatic soft top and a heated
glass rear window. And from April 2006 the **Z4 M Coupé**, the E86, with a fixed roof that dips down
the middle — BMW's own press material compared that channel to the Zagato coupés of the fifties. Under
both, the same engine, the same gearbox, the same brakes and the same rear axle.

### The engine

The **S54B32**: 3,246 cc, bore and stroke 87 × 91 mm, 11.5:1 compression, **343 PS at 7,900 rpm** and a
limiter at **8,000** — in Europe exactly the M3's figure. In the US the Z4 M is rated at 330 horsepower,
three fewer than the American M3, and BMW's US press kit puts that down to the exhaust, which has to fit
the Z4's much tighter underbody.

It is not a tuned version of the ordinary BMW six. The block is **cast iron** under an aluminium head —
BMW chose iron to reach 3.2 litres without lengthening the block. There is **an individual throttle for
each cylinder**, opened by an electric motor through a small gearbox. **Double VANOS** varies the timing of
both camshafts, and it has its own high-pressure pump — up to 120 bar, driven by the exhaust camshaft and fed
with engine oil — rather than relying on the oil pump. The valves are opened by what BMW calls *"extra-light
finger-type rocker arms"* with no hydraulic adjusters, so the valve clearance is something a workshop checks
rather than something the engine looks after itself.
And the oil system is a semi-dry sump with a scavenge pump, because, in BMW's words, *"particularly in
hard cornering to the left, it is critical to ensure return of oil to the pan."*

Hold on to that last sentence. It is why this guide asks not only what oil the car has had, but how it has been driven.

### What the M division changed around it

This is the part that makes a Z4 M a different car from a Z4 3.0si with the right bumpers, and it is
longer than most people expect:

- **The steering.** Every other Z4 has electric power steering. The M has *"essentially the M3 steering
  system"* — the M3's hydraulically assisted rack, and a pump of its own.
- **The gearbox.** A six-speed manual, the **ZF Type H** — not the Getrag of the M3 — and it was the
  only one. There was no SMG and no automatic.
- **The differential.** The **M Variable Differential Lock**, a limited-slip unit developed with GKN in
  which a viscous shear pump loads a multi-plate clutch, in the same heavy-duty size as the M3's, on a rear subframe that BMW describes as
  *"larger and stronger"*, with the M3's wheel bearings, central links and anti-roll bar arrangement.
- **The brakes.** Compound, cross-drilled, ventilated discs on all four wheels — **345 × 28 mm at the
  front and 328 × 20 mm at the rear**, two-piece, with an aluminium hat pinned to a cast-iron friction
  ring. BMW's US press kit calls it the brake system of the M3 Competition Package.
- **The wheels and tyres.** 18-inch M Double Spoke wheels with **225/45 ZR18 at the front and
  255/40 ZR18 at the rear**. Not run-flats, unlike the ordinary Z4, and no spare wheel — BMW's press kit
  says the M exhaust takes the space — so there is a sealant-and-compressor kit in the boot instead.
- **The front suspension.** A wider track, new forged-aluminium lower arms, and new steering knuckles.

### How many there are

**BMW's own figure for the Coupé is 4,581**, built between 2006 and 2008. For the Roadster BMW M gives
*"around 5,000"*. You will see other totals quoted — 4,275 Coupés appears on Wikipedia — and we use
the manufacturer's.

There was no Z4 M of the next generation. The E89 that replaced it in 2009 had a twin-turbo six at the
top of its range, and the top version came only with a dual-clutch gearbox. In December 2008 CAR magazine called the Z4 M *"this
iconic straight six's swansong"*, and that is a fair way of putting it.

### How the figures in this guide work

**How much work each job is, not what it costs.** Every point in the buying guide carries an effort — an
hour or two, half a day, a day, two or three days, or a week or more in the workshop — plus a line
saying whether the money sits in the part or in getting to it. Where a documented hour count exists for
this car, that is there too.

**There are no prices, and that is deliberate.** What a job costs depends on which country you are in
and which workshop you walk into, so a figure we cannot verify is worse than no figure. If you want an amount, ask any workshop one question — *what is your hourly rate?* — and every hour in the
buying guide becomes your own number, in your own currency.

None of this is advice about one particular car, because we have not seen the car you are looking at.
Have every one of them inspected before you buy, by someone who knows this engine.

---

---

## 2 · The six questions that decide whether *this* car is a good buy

These cars are now between eighteen and twenty years old, and on this model the paperwork matters
more than on almost anything else of its era. Six questions.

**1 · The oil — and therefore the bearings.**
The rod bearings are the most discussed item on this engine, and the one where the history matters more
than the mileage. BMW gives no replacement interval; specialists do recommend one. But the interval is
not the story. BMW's service information specifies a particular BMW M oil for every S54, specialists
advise changing it well inside what the service display allows, and BMW built the engine with a semi-dry sump because, in its
own words, *"in hard cornering to the left, it is critical to ensure return of oil to the pan."* So the question is not only "have they been done". It is **what oil
has gone in, how often, and how the car has been driven.**

**2 · The exhaust camshaft hub — has anybody looked?**
Every S54 has one, the M3's included, and most buyers have never heard of it. Redish Motorsport, a UK Z4 M
specialist, checks it as part of their pre-purchase inspection. It drives the VANOS pump, it can break, and in rare cases a broken
piece takes more of the engine with it. It cannot be seen at an ordinary viewing — which is why the inspection is
something you arrange before you agree a price, not after. What that inspection involves is in the
buying guide.

**3 · Which VANOS problem, if any?**
The double VANOS on this engine fails in more than one way, and the different failures have different
repairs and very different bills. Telling them apart is a job for somebody who knows this engine — and
knowing that there is more than one possible answer is what stops you
paying for the wrong repair.

**4 · The running-in inspection — and the myth around it.**
BMW asked every owner to bring the car back at 1,200 miles (2,000 km) for a running-in inspection. You
will read that it swapped out a special running-in oil, and that a car without it should be walked away
from. Not every source agrees. What it tells you, and what its absence does not, is in the buying
guide.

**5 · The back of the car — and why it is not the M3's problem.**
The M3 E46 that gave this car its engine is famous for its rear subframe tearing out of the floor. That is
not this car's story: we have found no documented case on a Z4 M. The back of this car has questions of
its own — the differential and the driveshafts first among them.

**6 · Roadster or Coupé — and what each one asks of you.**
The Roadster's roof is a mechanism with a weak point that is largely preventable if you know where to
look. The Coupé has one known place where it rusts, and Autocar's buying guide calls it *"the only place Z4 Ms
rot."* Both take five minutes to check, and both are easy to miss.

### What the answers add up to

On a well-documented car, where the oil has been looked after and the inspection has been done, an owner gets
through **mostly small jobs in the first two years** — an hour or two at a time, a few half-days, and
none of the heavy ones. The heavy ones on this car are few and they are known: the bearings, the VANOS,
and occasionally the differential. That is something you can plan for, rather than a bill that ambushes you.

That is only useful if you know what it is made of. The buying guide takes each of these six apart, adds
the things that are simply twenty years old, and says for each one how much work it is, what tells you about
it at a viewing, and whether it has to be done now or can wait. It comes with a card you print and take with you, in the order you do it, including the two moments at a viewing that come only
once.

---

---

## 3 · Which years, which specification

The Z4 M was built for less than three years. The Roadster went into production at the start of 2006,
after its debut at the Detroit motor show that January; the Coupé followed in April 2006. Both were
gone by the end of 2008.

**One engine, one gearbox.** The S54B32 and the six-speed manual, in every car. Two used-car guides
call the gearbox a Getrag; BMW's own press kit for the car says *"It is the ZF Type H"*, and we go with
the manufacturer. That makes the
specification question simpler than on almost any other car in this series: there is no automatic to
avoid, no SMG to check, and no smaller engine sold under the same name.

**Two bodies, and they are not the same car to drive.** BMW gives the torsional stiffness of the Coupé
as **32,000 Nm per degree**; for the Z4 Roadster it quotes **14,500**, and Autocar reported in 2005 that
the M Roadster's shell had been given no extra bracing. The Coupé has its own spring and damper
settings to suit. The Roadster has the roof that goes down, and that is a mechanism with its own
chapter in the buying guide. In European trim the two weigh 1,485 kg (Roadster) and 1,495 kg (Coupé).

**European and American cars.** BMW quotes 343 PS in Europe and 330 horsepower in the US for the same engine.
Neither is better; know which one you are looking at, because it changes which documentation applies —
the owner's supplement quoted in this guide is the American edition.

**How to tell a real one.** Bumpers, wheels and badges can be bought for any Z4, so check the things that are built into the car rather than
bolted on: the engine code S54 on the paperwork or a VIN decode, four
exhaust tips in a rear bumper with a diffuser, a 9,000 rpm rev counter with an **oil temperature gauge in
its lower face**, a 300 km/h speedometer (180 mph on an American car), the M logo behind the side indicator, and cross-drilled discs
visible through the wheels. A real one has all of them.

**And one thing it does not have, which surprises people.** There is **no coolant temperature gauge** on
a Z4 M. The owner's supplement says so in as many words: the car *"is not equipped with a coolant
thermometer"* — there is a yellow warning lamp when the engine is too warm and a red one when it has
overheated, and the oil temperature gauge on the rev counter. That is why the cooling system is on the inspection card.

**Beyond that, look for a car nobody has modified.** Factory wheels, standard ride height, the original
exhaust. On a car with this engine, originality says more about how the car was looked after than about the owner's
taste — and a car that has been used on track has had its oil moved around in exactly the way the
bottom end of this engine dislikes.

---

## 4 · What it is worth

This is the hardest thing to establish on your own, and it does as much as anything to decide whether you buy well. We are not going to give you a price list — it varies by country and by month,
and an out-of-date number is worse than no number. We are going to give you the method.

**On this car, the history sets the price.** Two cars with the same mileage are not the same car if one has invoices for the oil, the running-in inspection and the bearings, and the other has a stamped
book and an owner who says everything has been done. The gap between them is usually larger than any difference in colour, body or mileage.

**There are three kinds of car for sale, and each one deserves a different offer.**

*The documented car.* Full history, invoices tied to readings, an owner who knows what was done and when.
Asking price at the top of the market, usually justified. What you are buying is the history.

*The tidy car with no paperwork.* Drives well, looks good, and the owner says it has always been
serviced. The hardest of the three, because the thing you most need to know — what has happened inside
the bottom end of the engine — is exactly the thing you cannot see.

*The project.* Known work, price adjusted to match. Be more careful here than you would be with a cheaper
car: a Z4 M with an unexplained knock is not a project, it is an engine.

**How to set the three against each other.** Take the asking price, work through the questions in this guide — and the lists in the buying guide, if you have it
— and add up what is coming in the first two years. Call that the entry price, and compare entry prices rather than
asking prices. On a car like this one the documented car wins that comparison more often than not.

**Price Roadsters and Coupés separately.** The comparison that matters is between two cars of the same
body.

**Where to look:** your country's big classified sites, the BMW M specialists, and the auction sites.
Follow the market for a month before you go and see anything. You do not need a list price; you need to know what is happening — which cars sell quickly, which sit for months, and at what
price.

---

## 5 · What it is actually like to own one

It is a short car with a long bonnet, and everything about it is direct. Car and Driver, testing the Roadster in 2006, found that turn-in *"is instantaneous and precise"*
and that the ride *"will tell the occupants the dimensions of every expansion joint and concrete patch
the tires encounter."* Both are true, and you will notice the second one first.

The engine is the same one that made the M3 E46. It is smooth and tractable low down and it changes
character above six thousand, and in a car this size you go there more often than you would in the M3.
There is a band of lights on the rev counter that tells you how far you may go while the engine is
still warming up, and on this engine it is worth obeying.

CAR, testing the Coupé, found *"so much traction you can nail the throttle in any gear in most
situations"* — and also wrote that *"as transmissions go this one's a clunker."* It is a mechanical-feeling
gearbox rather than a slick one; drive one before you decide whether that suits you.

**It is a usable thing, within limits.** Two seats, no spare wheel, and a boot that is small in the
Roadster and surprisingly practical in the Coupé, whose tailgate opens the whole rear of the roof.
BMW's figures are roughly 200 to 220 litres for the Roadster, depending on the roof, and up to 300 for
the Coupé.

**What it costs you in attention.** More than a modern car, and concentrated in the oil. Short
intervals, the right grade, and a habit of watching the oil temperature before you use the top of the
rev range. On this engine that is not fussiness; it is the single thing you control that affects the
most expensive component in the car.

**What it gives back.** A six that revs to 8,000 rpm with no turbocharger, in a car small enough to
use it on an ordinary road. That is not an investment, and this guide will not pretend it is. It is the
swansong of this engine, and once you have driven one you understand why people keep them.

---

---

## The buying guide — €24

Everything above is what the car is. This is what you check.

Six faults that belong to this engine, taken apart one by one, with
how much work each repair is and how to tell which of them you are looking at.
Twenty-nine 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. The one place the Coupé rusts, the weak point in the Roadster's roof, and why that chapter is short. Why the M3's famous subframe problem is not this car's, and what wears at the back instead — with the differential and the driveshafts at the top of a specialist's list. The viewing in thirteen 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 — eighty 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 twenty-nine looks like

**5 · A click from the dashboard at start-up**
**An hour or two** to diagnose · the repair depends on access to the flap

A service bulletin listed for the 2006–2008 Z4 M Roadster attributes it to *"mis-alignment of the fresh
air/recirculation flap gears."* It sounds worse than it is.

*Leave it.*

### And this is how the card reads

- [ ] 1 · Before anybody starts it
- [ ] 2 · The cold start · *do nothing else, and nobody revs it*
- [ ] 3 · The engine bay, cold
- [ ] 4 · Round the outside
- [ ] 5 · The boot, floor up
- [ ] 6 · Roadster: the roof, engine running · *hands clear*

### What €24 buys, put next to what it saves

The rod bearings are **two or three days** in the workshop on cheap parts — you pay for the access. The VANOS is **a day**, and what it costs depends on which of several repairs it needs. And the exhaust camshaft hub is **half a day** to look at and, in the rare case where a broken piece reaches the timing chain, can damage the engine. 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.
- Where the sources disagree — on the running-in inspection, on who made the gearbox, on how often the rod bearings need doing — it says so and shows you both, instead of picking the one that sounds better.
- 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. Eight of the
  twenty-nine 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.

[Buy the BMW Z4 M E85 / E86 guide — €24](https://lastrealengines.com/z4m-e85-e86/)

*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.*