W116

It is a fortunate fact of life for us old-car enthusiasts that even the most expensive and up-market cars almost invariably fall within our modest means sooner or later.

So the Mercedes-Benz W116 S-Class, frequently the chosen transport of wealthy industrialists, diplomats, government ministers - and even heads of state - is now well within the grasp of the enthusiast.

Never cheap to buy new (thanks to its high specification and a steadily rising Deutschmark), never cheap to run (fuel consumption is typically 15mpg or less) and, at the time, both difficult and expensive to maintain outside Germany, the W116 sold nearly half a million units in its seven-year production run.

But it was this very success which, ironically, contributed in no small part to the car's inexorable slide into bangerdom and the ultimate ignominy of the sub-£1000 smalls ad. It may not be a significantly better car, but a Rolls-Royce - even one that has seen better days - will always possess a certain exclusivity.

By the late '70s the W116's problem was that there were just too many around, too many to choose from - many of them falling apart because their second, third or fourth owners couldn't afford (or couldn't be bothered) to look after them.

But that's not something which need concern us. Car enthusiasts who appreciate fine engineering, elegant styling, legendary reliability, longevity and high levels of safety, can today take advantage of the fact that a car that would have cost at least £11,000 new in 1972 - the equivalent of over £90,000 today - is now worth £4000 or less.

Admittedly, you have to be very careful not to take on a real banger, one of those all-too-common cars which was already in a wreck by the time it was 10-years old but, we guarantee that by the time you've driven a good S-Class 25 miles, you'll consider any lesser car to be little more than a wheelbarrow.

Despite its impressive, carved from-the solid build-quality, the W116 is just as likely to rust as almost any other unitary-construction car built from pressed steel, so start your examination of any prospective purchase by looking for rust.

A certain amount of cosmetic corrosion is almost inevitable, but the large-scale rot to which neglected examples are surprisingly prone - as well as rust in one or two specific problem areas - really does render the car little more than scrap. Front wings rot round the wheelarch edges and at their bottom lower corners. Check the whole of each inner wing/flitch panel, and particularly their upper areas where they meet the outer wings. On the right hand side of the engine bay check the battery tray for corrosion - usually caused by fitting a cheap replacement battery which leaks acid fumes while it's on charge.

Make sure that the box-section on the inside of each inner wing, behind the shock absorber turret, is in perfect condition. These, like the nearby chassis legs which carry the steering box and suspension, are am=lmost impossible to repair.

Lower front valances suffer quite badly, eventually taking on the appearance and texture of wet papier-mâché, and problems here often spell the end of the chassis leg which extends outwards to the lower front corner of each front wing.

Sills can disintegrate in a big way. Don't worry unduly if it's just the outer skins which have failed, but do make sure that damage doesn't extend to the inner panel or even the edges of the floorpans themselves. Repairs are not impossible, or particularly complicated, but they will certainly be expensive.

Check the jacking points, too: they may be badly distorted where someone has tried to lift the car, or so rotten that they'll collapse the first time you try to change a wheel (Always use a trolley jack rather than the standard item, if possible).

Again repairs are by no means impossible at the front of the car, but deep-seated problems in the rear jacking points which also affect the vital rear subframe attachments - yet again render it little more than crusher-fodder. While you're under the car, look at the longitudinal chassis members for corrosion, particularly where they kick up over the rear axle.

Rear wheelarches rust in the spot-welded joins between the inner and outer panels. Replacement sections are available, though, and the metal work here is no more complex than it is on, say, a Ford Escort.

Lower rear wings take a real beating from flying stones thrown up by the wheels, the problem here compounded by rust which can form in the wells at the lower rear corners of the boot compartment. Again not too difficult to repair.

The bottom rear corners of the bootlid itself are often bubbling with rust - this whole panel seems particularly susceptible to condensation during prolonged periods of cold, wet weather - and you'll often find rust in the recess behind the flap cover of the fuel filler cap, usually caused by blocked drain holes.

Door bottoms suffer for much the same reason, but don't assume that a perfect-looking door is just that. Both the top front corners of the front doors and the top rear corners of the rears can rust away unseen, and astonishingly you'll sometimes find that the whole lower door framework immediately behind the interior trim has disintegrated.

At the rear it's not unusual to see the outer door skin and the inner frame separating where they kick up over the wheels. Check these areas carefully and/or budget for some second-hand replacements.

The rear windscreen surround is another rust-prone area which is awkward to deal with. Problems usually start behind or below the chrome strip running the width of the car below the glass, and the resulting holes are impossible to patch properly without removing the glass and adjacent interior trim.

Likewise the sunroof, where fitted, rusts around its edges, and the drain tubes either rust away and/or become dislodges. So water finds its way into the cabin and quickly damages the otherwise hard-wearing trim. In severe cases, it can even attack the floorpan.

There is a lot of brightwork on a W116 and, since both new and even second-hand replacement parts are expensive, it pays to check it all carefully - for damage if not necessarily for corrosion.

The characteristic radiator grille is extremely prone to dents from flying stones and careless parking and likewise the rather strange double-decker front and rear bumpers - which can also rust through from behind - twist quite easily to make even o=an otherwise tidy car look a mess. Good-quality second-hand replacements are the best answer.

All plating itself is of very high quality, although door handles and the bodies of the door mirrors can become pitted if the car has been neglected. Make sure that car has its full quota of badges (all models could be ordered without them if required) and also that the body-colour wheel trims are undamaged. Again, scruffy trims can make even a good car look like a real banger.

Check the big rectangular headlamps for cracked of stone-shipped lenses and, at the rear, make sure that the huge plastic sidelamp/indicator lamp covers - deeply ribbed in order to remain visible in bad weather - are intact. Both items are expensive.

Last but not least, remember that there's no excuse for a missing or damaged three-pointed star on the bonnet. (It's sing-loaded to avoid unnecessary injury to pedestrians, bu the way.) Replacements, even from official Mercedes-Benz agents, cost less than £20.

Interior trim is tough and durable, if somewhat austere for British taste. Seats come i special plastic-based material called MB-Tex, which is about as tough as rhino hide, a very '70s velour or cloth or, where ordered, real leather.

Check for the usual splits, tears, cigarette burns and sun or water damage (these two can make short work of the rear parcel shelf). take a good look at the carpets for muddy footprints which suggest a cavalier, couldn't-care-less attitude to the car - and at the headlining for ingrained smoke and Brylcreem.

Check the various plastic interior mouldings for splits or tell-tale dirt (dashboard, door pulls and so on), and make sure that the woodwork (which, despite its appearance, really is wood) is in good condition.

Finally, don't worry too much if the interior creaks like an ancient galleon in a stiff breeze. It's caused by the close proximity of so many plastic mouldings, particularly where the inner door frames meet the body itself, and apart from very careful adjustment of door gaps there's not a great deal you can do about it.

It's a measure of the W116's strength that, despite it complexity, relatively little goes seriously wrong with it mechanically. That's not to say that it will never break, or that serious problems won't cost big money to fix, but we're not talking XJ12's, or ageing DBS V8s here.

That said, your first priority should really be to find a car which has obviously been maintained more or less as Stuttgart intended and, ideally, with a service history to prove it. Despite the age of the car that's by no means impossible, either.

Since, by the car's very nature, third, fourth or fifth owners tend to be less affluent and perhaps less caring that the first, you have to be absolutely sure you're not taking on someone else's insoluble problems.

By far the majority of W116s were fitted with a V8 engine; only the 2.74-litre 280SE featured a straight-six. Both units - each with an aluminium cylinder block and head(s) are recognisably from the same manufacturer, though, and have similar strengths and weaknesses. (Which include the need for anti-freeze in the coolant all year round to prevent internal corrosion of the waterways and the subsequent silting up of the radiator).

Regular oil and filter changes are also vital to avoid the formation of sludge which will quickly block the oil feed to the hard-working valve-gear - double overhead camshafts in the six and a single overhead camshaft per cylinder bank in the V8. Ignore this precaution and you'll suffer from rapid wear of the cam lobes and bearings and, unless the problem is rectified quickly, a completely wrecked engine.

Both engines also suffer from fairly rapid timing-chain wear (a working life of as little as 40,000 miles is by no means unusual) which, because it is such a major (and expensive) task to put right, tends to simply be ignored, but only to a certain extent; chances are this will have been exceeded by the time you come on the scene.

The good news is that the chains rarely break, but the considerable extra noise they create is hardly keeping with the character of the car. To check the chains, open the bonnet and listen for a metallic thrashing from the front end of the block; sometimes you'll also hear the clanging of a really loose chain as it hits the aluminium casing...

Reckon about £150-200 plus £100 or so for the part from a competent independent specialist or as much as £600-700 plus parts from an official Mercedes agent.

Be warned, though, that relatively few of the latter will be too keen to work on older models, particularly if they've seen better days.

Apart from that, both engines are more of less unburstable. Worn valve guides and then pistons will usually be the first signs of terminal wear, but then you'll probably be up to the 175-200,000-mile mark - if not considerably higher. Even then only the signs of wear may be a slight reduction in performance and economy, of the merest hint of smoke in the exhaust.

Two hints may be useful, though: change the spark plugs as soon as the engine becomes even slightly reluctant to start first thing in the morning, and keep an eye on the temperature gauge in traffic during the summer. Overheating isn't an endemic problem as it is in cars like the XJ6 but, unless the auxiliary fan is working correctly, even a W116 can get a little warm.

All UK-specification engines, whether straight-six or V8, were fitted with fuel injection, a Bosch electronic system to begin with and later the mechanically controlled K-Jetronic system. (Only the 280S, never officially sold here, was equipped with carburettors.) Problems are few and far between and both systems work reliably for many thousands of miles.

Higher-milage cars sometimes have problems in their electronic control units (ECUs), though, in which case tested second-hand units are the only practical answer. New ones would cost almost as much - if not more - than the car is worth.

Likewise clean fuel is vital to the systems' overall efficiency. Filters must be changed regularly to avoid blockages and pressure drops which may cause fuel starvation or even serious engine damage such as holed pistons. Technical advice and spare parts should be available from a fuel injection specialist.

Most transmissions are automatic (three- or four-speed, depending on model) although 280S and 280SE both came with a four-speed manual unit as standard. Again, no real problems here: just make sure both types behave exactly as you'd expect them to, and in the case of the automatics that means perfectly smooth gear changes. Harshness and/or noise spell problems; either get the car checked by an expert, haggle over the price or walk away.

Any remaining running-gear problems derive from the car's considerable weight and performance. Driveline clonks are not uncommon on the 450SEL 6.9, for example, but they're not really a problem until they become very noticeable. They usually emanate from the final drive, but check the prop-shaft joints, too.

All front brake pads wear quickly, and you must watch for leaking callipers and worn discs at both front and rear - the wear caused by running the pads so low that the metal backing material is exposed. This may also lead to cracks in the callipers. The handbrake operates on rear discs and should work.

You can expect spectacular tyre wear, particularly at the front, if you drive the car as hard as its superb engine and chassis will encourage you to, but if it's really excessive it's worth having the suspension checked by an expert. Ball joints and tracking are the usual culprits, although misalignment from earlier accident damage may be a rather less palatable cause.

Be very critical of the steering when you test-drive any W116. The system was designed with what is known as zero-offset geometry to provide better steering feel and high-speed stability, the great steering effort required in such a system provided automatically by the standard power-assistance.

It is probably this which can wear out a steering box in as little as 50,000 miles, making the car about as directionally stable at speed as an aircraft with its tailplane shot off. Some adjustment of the box is possible, but more often than not a complete replacement will be necessary. New steering boxes cost over £400, so a second-hand one is the only sensible answer.

The hydro-pneumatic suspension system fitted as standard to the 6.9-litre cars is similar in principle to the Citroen CX and the earlier DS. It dispensed with the smaller-engined W116s' coil springs in favour of a fluid- and nitrogen-filled sphere at each corner, together with oil-filled struts and gas-filled suspension dampers.

Working pressure is provided by an engine-driven pump and the ride height is adjustable by up to 1.5 inches, even while the car is moving. As a bonus the system is entirely self-levelling, too: load the car to the gunwales, in other words, and still it will sit at exactly the right height for optimum comfort and safety.

Problems are rare if the system has been maintained properly - which means removing the spheres and recharging them every two or three years, or replacing them when they are beyond help, and regularly changing the hydraulic fluid.

If the suspension is as flat as the proverbial pancake, talk to Citroen experts and you'll be able to get it working again for far less than Mercedes' prices.