Free guide · 1995–1998 · M104, M119, M120
Mercedes S-Class W140: 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
The S-Class that became a story. Built as a saloon from early 1991 to September 1998 and as a coupé from October 1992 to September 1998; this guide covers 1995 to 1998.
In those years the saloon came with the M104 straight six in the S 280 and S 320, the M119 V8 in the S 420 and S 500, or the M120 6.0 V12 in the S 600, alongside two diesels this guide does not cover. The coupé was only ever a V8 or a V12: the S 420, S 500 and S 600 Coupé, renamed CL 420, CL 500 and CL 600 in June 1996.
What is unusual about it, specifically
Double glazing. Not tinted glass — two panes, for silence. Doors that pull themselves the last centimetre shut, on cars that have the system. A twelve-cylinder engine that nobody had asked for. It was designed as though the question of what it cost to build would be answered later.
It is, famously, the car people point at when they say Mercedes never again let engineering run that far ahead of the accountants. We are not going to dress that up as a fact — it is the reputation the car has, and reputations are not sources. What is a fact is what is in it.
One piece of genuinely good news, before the rest
The wiring problem everyone warns you about is concentrated in the earlier cars.
The W140 is known for an engine loom whose insulation breaks down: it goes brittle, crumbles off the wires, and produces electrical faults that nobody can reproduce. It is a problem of the early production, but where it ends is not settled — we found no Mercedes document that gives a date. So the year shifts the odds, and the check settles it.
That does not make a late W140 immune, and you should still check. But it is free to check, and the buying guide tells you how in one sentence.
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.
The six questions that decide whether this car is a good buy
1 · What year is it, exactly?
1995 and later is what this guide is about. On the wiring problem it shifts the odds without clearing the car — and the year on the paperwork is not always the year that matters.
2 · Has the engine loom ever been replaced, and is there an invoice?
On any year, a documented replacement is the best answer you can get.
3 · On a V8: is there any paperwork about the timing chain and its guides?
The plastic guides are the known wear item. There is no agreed interval, so what you want is a date and an inspection, not a number.
4 · Does it have rear level control, and may I load the boot and watch what the back does?
Standard on the S 600, an option on the sixes and V8s. Where it is fitted, two minutes tell you whether it still holds its height.
5 · Do the two climate zones still work independently?
Knowable in the car park — how to test it without being fooled is in the buying guide.
6 · How often is it driven, and when was it last out?
A car with this much electronics that stands produces faults that a car that is used does not.
Which years, which specification
Saloon from early 1991, coupé from October 1992, both until September 1998. This guide covers 1995 onward: the second half, with the odds on the wiring shifted in your favour, and with the 1994 facelift behind it.
Which engine. The S 320 (or the smaller S 280) with the M104 straight six is the one to own if you want to use the car — smooth, simpler, and it does not ask for twelve of everything. The S 500 (or the S 420) with the M119 V8 is what most people picture. The S 600 with the M120 V12 is magnificent and every job on it costs more, because access is poor and there are two of most things.
What the chapters that follow are actually about. On a six, this is a guide about a wiring loom, and about the rear level control if the car has it. On a V8, the timing chain joins in. On a V12, which has the level control as standard, everything in here is true and costs more.
What it is worth
Not in money, but in the only currency that matters when you are standing next to one.
A W140 is bought as an old saloon and repaired as a flagship. The value of a specific car sits in three answers, and none of them is the mileage:
- what state the loom is in, and
- on a V8, what paperwork exists for the chain and its guides, and
- whether the car is used or stored.
A late car with a good loom, a documented engine and a folder is worth substantially more than its advert suggests. A cheap one with none of those is the same car with the bills still in front of it.
What it is actually like to own one
Very quiet, and much bigger than it looks in photographs.
The double glazing is not a gimmick; it is the reason a W140 at speed sounds like a room rather than a car. The six is smooth and unstressed. The V8 makes the size disappear. The V12 does that again, twice as expensively.
What it asks in return is that you use it. Electronics that sit develop faults; hydraulics that never move seize.
The honest summary: a W140 is a flagship for the money of a used mid-size saloon, and the cheap ones are cheap for reasons that are knowable in an hour with the bonnet open.
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 thirty 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. What a W140 shell does with age, and where to look for damp. Why the year shifts the odds on the wiring loom without settling them, and why you ask how a W140 has been used, not only how far it has gone. The viewing in nine steps, including the three 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
5 · Misting between the double-glazed panes
Half a day per window · in the glass The bodyshell chapter. Two panes mean a seal, and seals of this age can fail. Cosmetic until it annoys you, and visible every drive.
Now, by looking at each window against the light.
And this is how the card reads
- Standing, before you start it
- The cold start
- On the move
What €24 buys, put next to what it saves
On the V8 the plastic timing-chain guides are the known wear item, and reaching them is two or three days of labour. It is also free to check at a viewing, and the guide tells you how. 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 refuses to give you a replacement interval for the V8 timing chain, and says why: the figures you will find contradict each other and come from forums. It gives you a listening point and a question instead.
- 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.