Buyers guide to the W126C SEC 1981-1991

Advice on buying a W126C SEC 1981-1991

Revised 2010 02 14


  • Check the ABS function (malfunctioning sensors)
  • Corrosion in the trunk under rearwindow
  • Tempomat (Cruise control) function, no surging
  • Klima/AC check so it gets cold
  • If steeringwheel is adjustable check the function
  • See to it that all windows move up and down without any problem
  • make sure that sunroof will move in all directions
  • Check all warninglights that they glow when engine is shut off, and that they “go out” when the engine is started (the SRS can/shall be somewhat slower than the others)
  • There are NO “Bad” year on the W126 to watch out for.
  • Rear window delamination, watch the corners. rearwindows dont come cheap (app. -1300).

September 1981 at the Geneva auto salon the Mercedes-Benz W126C, SEC model was presented. The engine alternatives offered from the beginning was:

  • 380SEC V8 OHC 205hp (in Sweden)
  • 500SEC V8 OHC 231hp (in Sweden)
1986 there was a major update, a facelift, then the engine alternatives 420 and 560 was presented.
  • 420 V8 4196cc  218hp (in Sweden)
  • 560 V8 5547cc 286hp (in Sweden)
With the presentation of the 420 engine the 380 engine was taken out of production. Another change that took place with the facelift was that the bumpers and the side got then new flat design.
The 500 engine had 2 catalysator alternatives:
  • 150kw 231hp and
  • 170kw 265hp
As far as i know the 560 engine had 3 different engines:
  • 200 kw 274hp cat.
  • 205 kw 286hp cat.
  • 220 kw 300hp without cat.

560SEC (US market):

1986 A much-improved W126 coupe is launched with the following new/revised additions:

* Driver’s side airbag now standard instead of optional

* An all-new climate control system with re-circulation mode

* Sunroof tilt/slide mechanism relocated to the roof header panel

* Revised map lights

* A new Becker Grand Prix radio

* Newer center console with revised power window switches

* Newer VDO gauges with smaller lettering and brighter orange reflectivity

* Driver’s knee bolster

* 5.6L engine producing 238hp, 279ft. lbs. of torque

* 2.47:1 rear axle ratio with limited-slip

* Standard ABS braking system

* Revised EGR system (“check engine light”) and engine diagnostics were improved in 1989.

* Newer Bosch K-Jetronic fuel injection system

* 15″ 15-slot wheels and larger tires

* Different front brake caliper design

* Upgraded cruise control system (more reliable)

* Revised catalytic converters

* Flush mounted headlamps with headlamp washers/wipers

* Standard heated seats

* Smooth side moldings

* Smooth rocker panels with concealed jack points

* Power antenna circuitry is revised slightly

* Power telescoping steering wheel

* Power headrests and 2-position seat and steering wheel memory

* Revised rubber bushings and mounts for the rear differential

* Available rear power sunshade

* Dual-tone horns switchable from the dashboard

1987: ditto to 1986 model with revised mounting bolts for air cleaner housing

1988: an all-new 100w 10-speaker sound system with door speakers (6.5″) and multi-channel amplifiers mounted behind the rear seatbacks.

1989: a complete all-new interior with folded leather door panels, folded leather rear-side panels, ll-new seats front and back with larger side bolsters, revised EGR re-circulation system (“check engine light”) and engine diagnostics were improved, standard passenger-side airbag, passenger-side knee bolster, center console storage compartment with locking key and burl wood roll-top finish, higher wattage heated seats (from 90w to120w), higher capacity rear defroster.

1990: Burl wood storage compartment between rear seats (under the armrest)

1991: Addition of ASR (anti-slip regulation) traction control is made available as an optional extra

Buyer’s Guide to the W126 SEC- Looking for an SEC?

Don’t be in a hurry! There are lots of nice ones out there. Options include 4 place rear seating in sedans, metallic paint and velour seats (few US buyers opted for) as well as front seat lumbar support thing and the electric rear window sunshade (rare).

Colors I have noticed and recall (there could be more) are gloss black, pearl black, cabernet, lapis blue, nautical blue, white, cream, signal red, gold, silver, anthracite (gunmetal gray), smoke silver. 1986 cars on have basically the same equipment as up to 1991 except dual airbags came out in ’89 and ASR in ’91 I think ASR is not a necessary option.

The largest selection, best kept, rust free examples will be found in Southern California, especially Los Angeles. The large selection there gives you a better price break too. The S class is the “staff car” down there. When you are ready don’t forget to ask for Carfax report, VMI from the dealer, and get the car inspected.

Fewer and fewer are showing up on MB dealers lots, don’t forget they have slid out the bottom of the Kelly Blue book. Typical problem areas are the notorious Becker radio, the power window and Air conditioning. Subtract from the price if the AC doesn’t work. Other than that, the cars are pretty bulletproof, but parts are a little expensive, especially the aluminum trunk and hood.

A stock 560 SEC goes 0 to 60 in 6.9 to 7.1 seconds. But they respond well to after market mods, like lowering and AMG exhaust. However if I were you I would look for one in stock condition with all books stamped, and records available.

First, there is no “bad” year from 1985 to 1991. You need to be aware of the differences, such as the 1984-85 (500) motor is substantially slower than the 86-91 which would have the 560 motor. If you must have the 1985 motor you may save money if you would like to buy one in the 85 year. Will be cheaper but there are reasons- lots of them. Thus, basically any 86 to 91 car will be a US model, for the gray market basically ceased to exist in 1986.

SO, the first thing you need to do is to take a realistic look at your budget. How much do you have to spend, here: The lowest end, -12k will get you a good 85 with high miles.

On the other end, out here a 1990 SEC with 7,000 actual miles, so new it still had traces of cosmoline on the motor, went on the market here in San Jose in California for and it sold in 3 hours to a fellow in Chicago who bought it for the asking price, he jumped on a plane and came and got it.

That said, you will probably need to find out where your budget will fit. With a car like this, the general advice seems to be that you should pay at the beginning, the most-for the best-you can afford, i.e., the newest, best condition one you can possibly afford. The reason for that is that a bargain can very quickly prove to be no bargain at all if you get into extensive repairs right away.

To this end, perhaps ideal would be a car in stock condition, maintained by a fussy single owner with ALL books and records.

Don’t forget to run a CARFAX report on the car, ( on the internet), ask the dealer for a Vehicle Master Inquiry on it – to show all repairs done at a dealer, under warranty, then you should call 1-800-For Mercedes and ask them to give you a copy of the original window sticker-that will also show you the dealer first delivered to.

Look in the books and records and call up the people who worked on the car. If you are lucky you can get to look at the actual repair orders, sometimes they are still around.

I have told people over and over I believe the safest source to look for cars is Los Angeles because they are best kept, the market is saturated with them, the body and repair shops are generally most competent, and the weather is most agreeable for preserving them, and the prices are lowest and

the selection is widest because there are so many of them around down there. The very very best ones even still are occasionally seen at Mercedes dealers down there.

As far as problem areas there are few. When I did join the list I did ask around and read the buyers guide and this is what I know.

Problem areas are…

These cars are generally bulletproof if you take care of them. If you don’t, they will cost a mint to fix. Therefore, be sure you get one that can be documented to have been well kept, and you do the same.

  • Biggest one of all is the air conditioning. If the car you are looking at, the AC doesn’t work, I would IMMEDIATELY subtract off the price, because it could cost this much to fix. Even if-in some cases, all it needs is a new fuse. You can almost expect a problem here. Don’t be surprised.
  • The Becker radios are awful. These are the factory radio and I would dump one immediately for a nice Alpine with a CD trunk loader. Or other equivalent.
  • There are sometimes trouble in the power door locks and vacuum system. Don’t be surprised about that.
  • There is danger of upper hose neck breakage on the original equipment radiators. This is MORE likely to occur if at any time NON Mercedes coolant was used. Don’t forget these are plastic radiators and they can’t withstand certain chemicals in other coolants. Plus, the necks on OEM radiators are not reinforced. Therefore, consider these consumable and due to be replaced at 100,000 miles.
  • The seal around the rear window fails, leaking water into the boot and rusting the metal below the rear window.What to watch for more:

I would have the following checked & then speak with the service person & have them FAX you the results, as well (BE PICKY/ANAL):

  • Interior… fading, rips, tears, fit & finish of parts, condition of carpeting, checking for any wear & full functions of seats, headrests, windows, anything & everything… period
  • Exterior… paint & body condition… full inspection for rust, dings and fully functioning sunroof, doors and shape of wheels & tires, front end parts, and if any leaks are present
  • Engine… leaks, has it been steam-cleaned?… compression check, fluids checked, rust under hood?
  • Driving… shifts ok, no smoke at tailpipe when cold & upon acceleration, A/C works & is cold, brakes in good shape, any squeaks, rattles?
  • Are there records with it to give you an idea of its servicing?
  • Are you having it shipped, or are you close enough to get there & then drive it home? Use their recommendation on shipping and check the back of The Star for companies that ship cars. Sometimes, it may be easier & cheaper to fly there & drive it home.
  • If car is warranted, then many or all repairs would be under the warranty. Take advantage of that
  • Try to speak to the former owner… know where it came from & why it was being sold
  • Check with your local dealer for extended warranty details (cost, what level of repair it has to be in… what might need to be spent by you or the orig. warranty to get it under a new one… and, then enjoy it)

My father’s looking closely at a 1990 560SEL, and it’s only got about 80,000 miles on the clock. Looks to be in very good shape (no PPI yet, though)

You’ll want a PPI for sure. Before going that far, check: Engine and transmission oil. Both should be clean. Look at the air filter element. Should be clean. Check coolant hoses and water pump for signs of leaks, band-aid repairs. There should not be oil plastered on anything.

Engine compartments on these cars stay quite clean. Look underneath for oil. Some light seepage at rear main seal is normal (black on bottom of bell housing) but should be no great quantity. Transmission should be dry (no transmission oil on bell housing or at rear). Rear axle final drive (differential) should be dry.

Start car with closed throttle. Should start right up on 8 cylinders, rev up, and settle down to a smooth idle. Any “clack-clack” from the valve train is a sign of serious trouble (Camshafts).

Run away from this. Transmission should engage in both forward and reverse smoothly. Pause in neutral before shifting direction. You should feel engagement start immediately, and lock-in in about a second. Steering should be tight. Brakes should have firm pedal.

  • Check for abnormal tire wear. (alignment? loose suspension parts? check rears as well as fronts)
  • Drive car. Shifts should be positive, not “soggy.” Try kickback/kickdown (downshift on throttle opening). Should not run away when shifting. I think the ’90 still is second gear start. Check kickdown to first, 1-2 upshift may be abrupt
  • Check steering—should go straight ahead and not drift to one side; wheel should be centered. Go over some bumps and listen for loose parts (open the driver’s window)
  • Check brakes—no pull from any wheel on modest stops. Do a panic stop from 25 mph. (warn passengers, check for traffic behind) to check
  • ABS. No wheel should lock up, and stops should be true without pulling (may notice a “grinding” or vibration as the ABS does its thing)
  • Check cruise control. Should engage positively above 40 km/h, accelerate and decelerate smoothly, hold speed without hunting (not too difficult to fix, but famous for giving up)
  • Check heater/AC controls. Open hood, put on normal (down arrow only filled in). Dial temp down and check that A/C clutch engages. Put on EC and check that clutch disengages. On cooling check that air comes from center and both side vents. Set control for heat and check that center vent shuts off.
  • Work all the seat adjuster knobs and make sure that all the parts operate. Headrest up/down, seat back forward/back, seat rear and seat front (independent—push pull the ends of the knob) both go up and down. Repeat on both sides, and check that rear seat adjuster functions
  • Check steering wheel in-out adjuster (switch on column, left side)
  • Check all window switches for up-down without grinding or binding
  • Check radio, and see that antenna goes up and down when switching radio on and off
  • Check dash panel warning lights—should be lit with engine stopped, all except SRS go out when started, SRS goes out in less than 10 seconds
  • If you feel it passes these preliminary checks, then take it to a pro and spend some money to get a proper pre-purchase inspection. Most pros will just look at the car and listen to it running, and decide whether to go further. Don’t be chagrined if your pro looks at it and declares it a “toad” (Stu’s term)—-there is a certain 6th sense “savvy” that one gets from doing this sort of thing regularly.
  • The most expensive fix is camshafts and leaking head gaskets.. Examine the cam lobes and the rockers and examine the head gasket parting lines for oil leaks during the pre purchase inspection..
  • Check floor pans, trunk and back seat (if installed) or back access panel on floor for rust. Don’t be afraid to pull up the carpet a bit to check. If the foam carpet padding is wet, it wasn’t “garage kept” (doesn’t sound like that’ll be a problem)
  • Check steering free play
  • Rotors and pad of course (maybe the safety stuff should be prioritized)
  • Check under battery for corrosion of the box.
  • Put the hammer down on the highway and look for smoke, let it get good and warmed up first
  • Check out the muffler. If it’s original, it may be wearing thin
  • Check for leaks after the highway run. . .
  • Thorough check of all rubber door, window, trunk seals. They may look good, but may be dried out and non functional

First, take your time. I don’t know where you live, but around here it is still possible to find terrific examples. While a dealership might not have one available for you on a given day, take your time & you’ll end up seeing a number of them.

Second, Ignore how fantastic the car looks cosmetically. The paint and interior materials are of such high quality that an amateur with 6 hours available on a Saturday can make a true wreck of a car look great. Six hours at a professional detailer & you’d swear that that ‘pig in waiting’ has never seen daylight, like it just arrived from Germany, gorgeous, breath-taking, looks like it’s never been sat in.

Third, make sure the car has well documented records of all service. If somehow they’ve errr… become separated from the car’, separate yourself from the premises. These are MB’s flagship model, therefore the most complicated version. I’ve seen people who buy them and then can’t afford to maintain them, so oil changes and little things get put off, in addition to the big things.

These cars are your money pits. According to Stu Ritter, if oil changes have been neglected wear of the camshafts can occur, and timing chain stretch will be greater. A professional familiar with these engines will know exactly what you are talking about. While replacing a timing chain isn’t too bad, be seated when he tells you about replacing the camshafts and related work.

Fourth, have the car inspected by a professional who is specifically very familiar with ’90 – ’91 560SEL’s. Have them go over the car with a fine tooth comb, including a compression check. This may cost you but if my experience is at all relevant, you will uncover much more than that in needed repairs which then is a very strong negotiation point in arriving at a final price.

Life expectancy? I own this car and a pair of 123 chassis turbo diesels which currently each have over 200k miles on them. Do I expect my 560SEL to match the life expectancy of my 123’s??? Probably not, but there’s still a huge amount of longevity in these cars if maintained properly.

I tend to be overboard in how I maintain my cars, and based on how it’s running, I’m hoping to get 250,000 miles from the engine before any major work is required. While the trans operates great, I’ll be pleasantly surprised if it makes it to 250k, although Stu Ritter has remarked that he has clients who’s trans last that long or longer.

At 250k if I find that the engine and trans are toast, then it’s a decision, as I suspect I could install a rebuilt engine and trans from MB for k and be ready for another 150k miles.

While that sounds like a lot, I could spend k on a used Taurus and I doubt I’d get an additional 150k miles out of it with the same degree of reliability and safety. Knocking on wood, my 560 is a wonderful car. Things need to be tended to from time to time, with me budgeting a year towards repairs / improvements, and so far it’s been wonderful experience.

In addition to being an incredible car to drive, I feel very safe using it to drive family and friends as I consider it a very safe car. It also has it’s downsides, but overall I’ve found it to have exceeded my expectations and plan to own it for many more years. Hope this helps.

This car is a rather old car that was expensive to purchase and is expensive to maintain. Further, it is likely that it will need significant repairs done in the near future if they have not already been done.

Some potential examples of *repairs* and *not* failures (and *not* an exhaustive list by any means):

  • A/C compressor — or more for a non-DIYer
  • Climate control problems — or more for a non-DIYer
  • Cruise control problems — for a non-DIYer
  • Front suspension rebuild — or more for a non-DIYer
  • Rear suspension subframe mounts and differential mounts — for a non-DIYer
  • Transmission rebuild — -2500 for a non-DIYer

Some potential examples of *failures*:

  • Radiator neck breaking — unless car is significantly overheated, then – 10,000 for a rebuilt engine
  • Cracked head — or so

And these are NOT California prices they are Texas estimates which are much cheaper:

Purchase a car that has COMPLETELY up to date service books/records only. There are simply too many of these cars on the market today – which have been meticulously maintained, and preferably at the dealer – to buy one that has been even remotely neglected. If the car you’re considering doesn’t have complete books that are up to the minute, here’s a turnkey solution:

Go to several authorized dealers nearby in person and say hello to the new and preowned sales people. Tell them you’re in the market for a nicely or perfectly maintained w126. Tell them what colors you’d like and the mileage you’ll consider. Put it all down for them on a piece of paper with your name and number.

They’ll know you’re serious this way. Next, tell them you’d like their help in finding a nice car and that you’d be happy to pay them, say, or if you buy a car they locate for you. Also, tell them that you are serious about buying by XX and XX date, and that if one of their w126 clients would like to come into the showroom to look at a newer or new Mercedes … that you’d be happy to meet them at the dealership to examine their trade-in. The word ‘new’ should perk up their ears.

If you do the above, the sales person will take you seriously and most likely contact several of their clients to alert them of a prime opportunity to ‘move-up’ and purchase or lease newer car. A good sales person would be foolish not to consult his or her Rolodex for existing w126 owners who may now be ready to do so. Perhaps an older couple who haven’t driven much but are ready for a w140 or a 2000 “S”?

You’ll be presenting a wonderful and opportune moment for any good sales person to do some win-win-win work — and you’ll get what you want and deserve from a w126 in the bargain.

The engine in the 560 is a 5.6 liter v8 and the engine in the 420 has a 4.2 liter v8. The 420 is fast! The 560 is faster. Both are heavy on the gas if you are heavy on the pedal. While keeping an eye on your cash, consider very seriously taking the extra few thousand you’d spend on the 560 – to buy a 420 that is in even better condition.

Both of these cars are BEAUTIFUL to own and drive – provided they don’t plague you with annoying (and costly) problems that are CERTAIN to arise if the books are not up to date.

I think we’d all be surprised by the number of people driving badly maintained “S” class cars. They may still look nice on the outside, but get under the hood or inside the cabin of most w126’s on the road today … and I’d bet half of them have inoperative A/C, switch gear and troubled mechanicals.

Not from poor engineering! But from a lack of maintenance by able wallets. The back muffler on my ’87 420 was CDN at the dealer several years ago. And if you put after-market stuff on the car it’s no longer a true Benz and will most likely perform sub-optimally.

The question is – do you want a real Mercedes, or a problem on wheels for show? If you go with a well cared for w126, books all up to date, I assure you this car will impress you Every time you start and drive it. In my opinion — which is likely shared by many 126 owners here, if not all them — the w126 is a phenomenal car that makes most 2000 model year vehicles (by other manufacturers) pale in comparison!

The w126 suspension is phenomenal (still readily impresses me after 10 years), the engines are superb, high speed steering is breathtaking and perfect, high speed stability is even more breathtaking, the engineering of the 126 is prized by all Benz mechanics as being some of the most trouble-free and superb that Benz may ever produce – just ask them.

Let’s face it, parts wear out. It’s only natural. The self leveling on the 560 has not been a problem. But yes, it will wear out – and cost you a goodly sum when it does as compared to simply replacing the shocks as you would on a 420 — an easy, inexpensive job. If you’re wondering if a 420 is less comfort able than a 560, the answer is no.

I’ve had 5 passengers in mine for numerous 1000 km trips with full luggage and the ride comfort is incomparable to any other car I’ve ever ridden in – save for a Rolls, Bentley, or w140. In fact, the heavier your load, the more comfortable the car is on highway runs. It just hunkers down and sticks to the road like glue – with exacting precision.

Long distance cruising in a fully laden S Class at speeds above 140 mph will very quickly impress you and turn you into a lifelong Benz lover. Try that in a 2000 Cadillac at 4 times the price of a ’90 S Class … You won’t be near as impressed or as comfortable.

You’ve probably already fallen in love with the 126 – just buy one that’s been wonderfully maintained (no ‘ghost’ owners, forget about the cars that are priced ‘too good to be true’) and the wonderful experience will last forever. What’s more, a pristine, all-original w126 with gleaming paint and wheels in factory condition is still perhaps the most elegant sedan on the road today.

P.S. If the tires need replacing at the time of purchase, this is an excellent opportunity to shod the car with new “V” or “VR” rated tires. “V” rated tires will make you a MUCH happier 126 owner. Plus, you can shave a few dollars off your purchase deal when you tell the seller the tires need replacing soon. If you’d like to hear more about my experience with great tires on the w126, please feel free to e-mail me and I’ll send you a copy of my recent post at the MBCA Discussion Forum.

Before buying my car I spoke to a person at Hatch & Sons who told me that starting in ’89 the camshafts had a harder surface and therefore weren’t as prone to failure, but I’ve never been able to confirm that point, so not sure if it’s correct or not.

These are great cars when well maintained, but complicated/expensive to fix when not, so just be extremely demanding about having a really thorough PPI done by a mechanic who has had years of experience working on 560’s, with a compression or leak down test.

Be very suspicious if it’s the least bit noisy or doesn’t drive & idle smoothly – when right, these cars are silent & smooth as glass. While it’s typical to see evidence of some dampness on the underside of these cars due to miles & years, anything beyond a slight dampness should put your radar on full alert.

And like any 126 chassis S class, the suspension should be quiet & as solid as a rock; the self-leveling hydraulic system on this car is wonderful. This was MB’s flagship model, therefore the most complicated version they had, but a car that puts a smile on my face every time I drive it.

There are many very well maintained examples of these cars around, so unless the provenance is good and all service records are available for your review showing not only normal O&F changes, but all the normal stuff that should have been fixed over the last 13 years, I’d be wary.

Maintenance Schedule

Yes, I am suggesting an aggressive maintenance schedule. It will save you in the long run. Based on my conversations with other Mercedes owners in questions posed to the lists I would do the following things:

  • Oil changed each 3,500 miles – for sure if dusty or city driving
  • Air filters and fuel filters (2 fuel filters) about each 15,000 miles
  • Auto trans fluid each 15k to 30k -depending on kind of driving
  • Brake fluid flush once a year or 12,000 miles whichever comes first. It really DOES get dirty but the std is so rigorous because of 150 mph panic stops on autobahn, I guess
  • Rear diff fluid each 30k, for models with LTD slip fluid – use the Mercedes Ltd slip diff fluid, it is 90w
  • Tune up: new plugs each15k or 30k whatever you feel is better
  • YES, renew even the power steering fluid and filter each 20 or 30k, this is not even in the owners manual but do it now or pay for a new pump later
  • Every 30k change the fluid in hydraulic rear suspension or else you risk big trouble on these. Motor mounts last at least 50k but should be watched
  • Wheel alignment perhaps each 12k – if necessary This may sound like a lot but it is preventative maintenance and you will be rewarded with a reliable car if you take care of it

Now then: I would shy away from one needing body work. This is super expensive to have done to the proper standard. Much more so than repairs.

Basically there are cosmetic interior changes beginning in 1989. I believe most models are fully equipped and that means ABS and airbags, I think in 88 or 89 they were dual but I am not sure. A model with a dual airbag won’t have a glove box, that is how you tell.

From memory, I recall that the options are few – they included on the 91, anyway, power rear electric rear window sunshade, velour (Few US customers wanted), metallic paint, reinforced seat frames and a lumbar support thing in the seats. For ’91 only you could order traction control- something I personally would not want. Make sure the car you buy has its tool kit, first aid kit and spare tire and jack in place.

There is mixed opinion about modifying the cars to handle well. Some believe Mercedes designed them to handle best with the springs, tires and wheels the car was supplied with, believing the suspension geometry was best this way. Others like the aggressive look and handling on a lowered car with wider bigger tires. My car was like this and I have grown over the years to enjoy the Eibach springs and 50 series tires.

I hope this helps. It is my opinion only, but at least it is a start. I have NEVER regretted buying this car-never- and it will save my life in a crash too. It is as unremarkable at 130 MPH as at 60 mph. (Don’t ask me how I know !!) Feels solid as a rock, I love the thunk of the doors as they shut. home.

I cannot believe I thought about a new Volvo 960 and a Lincoln Towncar when I was looking. This is definitely the ride for me. Plus, there is a dedicated following of owners to help with questions relating to my ownership of the car. To that end, you may contact me again. Hope this helps.

One thing I forgot, and it is important: Change the timing chain, tensioner & guide rails at 100,000 miles. If the chain stretches and breaks or jumps the rail (more often on the left side) it will cause a huge mess- a engine rebuild could be the result. More preventative maintenance…

More Maintenance Advice

At 65,000 miles you should check – and CHANGE also the rear diff and power steering fluid, if no proof they were changed within last 30k change it now. Same with Auto trans fluid and spark plugs. ORIGINAL. You should change the tensioner, timing chain and guide rails at 100,000 miles.

Behr radiator has unreinforced hose necks, they can crack and cause catastrophe. At about 75-100k just put in a replacement radiator, whole new radiator, view as a consumable item. The replacements have reinforced hose necks, so unlikely to be a problem again. These cars ask for a yearly brake fluid flush, radiator fluid ought to be changed every other year USE ONLY Mercedes coolant).

You can go3500 miles between oil changes, I would not go more than that though between them. I would start watching the motor mounts now and the steering damper too. Perhaps change them out at 100,000 miles. This may seem like a lot BUT if you care for the car well it ought to last you forever and look new all the time.

Major maintenance cycle every 30,000 miles, with a big one at 60,000, and lesser every 15,000. All of these should have been done “by the book.” Keep in mind that you are maintaining a car that cost something like K new. You can buy it a lot cheaper, but it still wants maintenance applicable to a K car.

Any major problems with the self leveling on this beast? None in particular. There is a hydraulic fluid tank and pump, using special hydraulic oil (all this I understand came from Citroen DS/ID technology), and the oil and filter want changing every so often. There are nitrogen spheres that give up the ghost after a while, but they are not that difficult to replace. Unfortunately, this type of system tends to baffle the Joe Average mechanic, and you’ll want to run it by someone who knows these cars inside out.

560SEC Model Run

Specs: Well, here goes the 560SEC run down:

1986 – A much-improved W126 coupe is launched with the following new/revised additions:
Driver’s side airbag now standard instead of optional
An all-new climate control system with re-circulation mode
Sunroof tilt/slide mechanism relocated to the roof header panel
Revised map lights
A new Becker Grand Prix radio
Newer center console with revised power window switches
Newer VDO gauges with smaller lettering and brighter orange reflectivity
Driver’s knee bolster
5.6L engine producing 238hp, 279ft. lbs. of torque
2.47:1 rear axle ratio with limited-slip
Standard ABS braking system
Revised EGR system
Newer Bosch K-Jetronic fuel injection system
15″ 15-slot wheels and larger tires
Different front brake caliper design
Upgraded cruise control system (more reliable)
Revised catalytic converters
Flush mounted headlamps with headlamp washers/wipers
Standard heated seats
Smooth side moldings
Smooth rocker panels with concealed jack points
Power antenna circuitry is revised slightly
Power telescoping steering wheel
Power headrests and 2-position seat and steering wheel memory
Revised rubber bushings and mounts for the rear differential
Available rear power sunshade
Dual-tone horns switchable from the dashboard
1987: ditto to 1986 model with revised mounting bolts for air cleaner housing
1988: an all-new 100w 10-speaker sound system with door speakers (6.5″) and multi-channel amplifiers mounted behind the rear seatbacks, lighted sunroof switch.
1989: a complete all-new interior with folded leather door panels, folded leather rear-side panels, all-new seats front and back with larger side bolsters, revised EGR re-circulation system, standard passenger-side airbag, passenger-side knee bolster, center console storage compartment with locking key and burl wood roll-top finish, higher wattage heated seats (from 90w to120w), higher capacity rear defroster.
1990: burl wood storage compartment between rear seats (under the armrest)
1991: addition of ASR (anti-slip regulation) traction control is made available as an optional extra, power antenna height adjustment switch removed

No differences in ride from 1986+ that is really very noticeable. The isolation of the rear differential from the sub-chassis of the car was a massive improvement in 1986. Reliability of the climate control and the cruise control systems where improved in 1986 as well. The EGR circuit (“check engine light”) and engine diagnostics were improved in 1989.

Otherwise, the cars are all virtually bulletproof. No major drawbacks to any particular years to be specific. Look car to car vs. year to year.

Some General Comments

Compared to modern day automobiles, these are big cars. They don’t have a “cabin,” they have a passenger compartment, and are one of the few automobiles that have legroom in the back seat for adults.

These cars are highway machines, and don’t really come into their own until you hit 65-70 mph. They seem quite sedate around town, but push on the “go” pedal—and it’ll go. This is no “funny little foreign car”—the engine is huge (338 CID) by modern standards, and with those overhead cams and the way it’s tuned, it’s made to be revved up to speeds that would blow apart most American V-8’s.

It’s also nobody’s econo-car—16-17 mpg on the highway, and that’s top-of-the-line premium petrol, not the cheap stuff. That 250KPH/155MPH speedometer is not “political promises”—the car will get almost all the way to the end of that range.

Ride and handling at low speeds will seem stiff and abrupt compared with Cadillac and Lincoln, but the car is sure-footed and quite comfortable at speeds that would be terrifying in said Cadillac or Lincoln. You are going to want good high-speed tires on a car like this (mine has new Michelin MXV’s).

These are not fussy or cantankerous beasts—-like the Beech Bonanza and Baron airplanes, they are not just “image,” but have serious substance under that image, and in the right hands (and with proper maintenance, most of which is “preventive”) they deliver the goods. If you want a real highway hauler, this is one to look at.

Courtesy of:

It is much better to buy a Mercedes Benz where everything is working from the beginning.
Such a car will cost you more but it is ALWAYS cheaper in the end as the repair costs are very seldom cheap on a Mercedes Benz S-Class A good looking and well maintained car is always the best investment in Mercedes Benz shopping.

“Take good care of your car, she deserves it”.

Mercedes W126 tips & tricks submitted by member: Tach erratic:
Loosen the small cap under the hood (on the fender) and put a rubber o-ring from a garden hose inside. Then re-screw the cap and it should fix the problem. If it happens again, replace this part (called a “tach amplifier”)

Rear heat vent blowing COLD air:
This is normal. The heat comes from under the seats. This vent is a ‘fresh air vent’. Make SURE it’s shut off all the way in winter — slide it to closed, then keep pushing hard until it ‘clicks’ into the off position. You’ll see what I mean when you do it. If it doesn’t click off, it will leak cold air.

Cruise control:
The amplifier under the dash dies. It’s by the parking brake pedal and is held in by a 10mm bolt. Either take it apart & re-solder connections OR send it to be rebuilt (about -200). Can’t do both– if you re-solder, they will NOT accept it as a core.. decide first!

Trunk leaks:
If it’s leaking from a “hidden” spot into the trunk wells, check three areas: 1)tail light can leak water in from the seal 2)antenna grommet can be bad and will leak 3)rear window gasket can leak in bottom corner. Hope it’s not #3 as this means there is rust under the gasket in this area (common) and needs to be cut out & fixed. It’s worse than you can see as it’s hidden by the gasket. Get in trunk & have someone spray with hose to find the leak.

Rear seat:
Easy to remove- find two tabs (may be colored red) at bottom of rear seat cushion. Push both tabs toward each other, lift front edge of seat and pull out. Seat back comes out by removing a few 10mm bolts at the bottom, then pull bottom away from car and lift straight up. WATCH out that the metal tabs on the bottom don’t scratch the car on the way out!

Back end of car steers itself:
Your sub-frame mounts are old. They can be easily replaced by making a tool out of threaded rod and some bolts, and using a couple of shop jacks. Spray the bolts 2 DAYS BEFORE with PB blaster and the job will be 100x easier! Search forums for more info on replacement

Fuse for trunk light and memory seats keeps blowing:
The wiring harness near the trunk hinge flexes all the time, and the wires have shorted. Pull the wires and electrical tape them, and you’ll be fine.

Window won’t move, but motor runs:
search forums for my post on “sliding jaw”. This can be replaced for and does not require any rivets if you use a bolt & nut like I did. Need to take off door panel, but it’s an easy job otherwise. MB window regulators and motors almost NEVER fail.

Voltage regulator:
Look at back of alternator, remove two flat screws with stubby screwdriver. Pull out (comes out at an angle, doesn’t pull straight out) and look at the length of the brushes (two rectangular rods with curved tips). 1″ = brand new, 1/4″=dead on roadside. Judge how bad yours are and replace. They’re and well worth it. Even if you don’t replace it, buy a spare for the trunk.

Replace them ALL before troubleshooting electrical problems. They look good but are NOT! I’ve had them fall apart in my hands even though they looked fine when in the fuse box. They’re cheap — buy a set and replace them all NOW and you’ll be fine for 10 years!

Front end clunk:
Could be a few things, but the tie rod ends and guide rod mounts are very common.

Rear end clunk:
Check the sway bar links, they make lots of noise!

Locked out of trunk:
if the trunk linkage becomes loose & sloppy, you can’t open it by pushing the button. Take a 2×4 about a foot long and hold it so one tip is on the trunk button. Whack the other tip with a hammer (seriously). The trunk should pop open. Make SURE the lock is unlocked first (you can lock & unlock the drivers door to make sure it is in the unlocked position).

This won’t work if something else is wrong with your trunk. Now pull off the top plastic cover and pull back the carpet. You can adjust the linkage from here. Make sure it works before closing the trunk!!

Rear brakes:
Make SURE you keep on top of the pad thickness. Once you’re down to about 20% pad or less, the pads will cock themselves in the caliper diagonally. Then the caliper seizes. You will know this happened when you pull the pads and can’t push the piston back into the caliper. It’s time for a rebuilt caliper at this point. I’d change the rear pads (they’re cheap and last for years!) when they’re down to 35-40% just to be safe.

Parking brake light stays on:
There was a recall for the parking brake cable on this car. It involves removing the entire cable from the pedal to the rear brakes, including a ton of labor. Here’s the easy fix: Put a wire tie around the parking brake pedal arm (near the top) and clip one end of a spring (from Home Depot) to it.

Clip the other end under the dash to keep the pedal pulled up. Everything works as normal, but the little bit of slack in the pedal is eliminated, so the light will stay off.

Dripping ATF:
Most likely this is the ATF lines going to the radiator (transmission cooler). Replace these lines if they’re dripping — you just need a crow’s foot wrench. You will know they are leaking if there is any ATF on the outside.

You can find these easily by looking at the bottom of your radiator (look from under the car) and find two hoses that look like they have a “spring” covering the outside. It looks like a hose with a piece of wire wrapped around in a coil-like shape. You’ll see what I mean.

Hood pad:
Buy a new hood pad but be CAREFUL how you install the new one. Search the forums — there is a special 3M glue and you MUST scrape off ALL the old gunk first. If not, you’ll be doing the job again in 2 weeks. Make sure to do it right the first time!

The MB battery is made by Interstate and this is the best battery for the car. Try an Interstate before buying anything else for this car!

Many opinions here, but Michelins have always been EXCELLENT for me on a number of these cars. One tire expert told me to remember the phrase “Michelins on Mercedes” because that’s all they recommend after years of being in the business.

Clunking from front end going over bumps:
Check your brake support bushings (search forums for info). These are common problem areas on the W126. If they haven’t been replaced, you will be changing them for sure.

Windows or seats not working:
The switch is dirty. Clean it out with contact cleaner or similar (TV tuner cleaner from Radio Shack works also). Most times the switch is just dirty. Keep working the switch back & forth while cleaning.

Radio scratchy noise in some speakers:
The fader (roller dial in the center console) corrodes a bit. Roll it back and forth as far as you can in each direction. I do this about every 3 months and the problem never reappears.

Use the original MB wipers (or buy a set if you have aftermarket blades). Some members have had great experiences with Anco blades, but I find the MB ones to work perfectly. You only replace the rubber in these blades (search forums for instructions on swapping blade rubber) and keep using the same blade “frame”.

Smearing windshield:
After trying a ton of things (bending wiper arms, new wiper blades, scrubbing windshield w/glass stripper, etc, etc.) I found a solution. Put about 6 drops of dishwashing soap into the washer reservoir with each gallon of washer fluid. Use a “degreasing” detergent like Dawn or one that says it “cuts grease” on the label.

Works perfectly (don’t worry, there are no suds with this little soap). Keeps my nozzles from clogging and keeps the windshield clean.

Stereo installation:
Do NOT screw an amp to the rear wall of the trunk like you can do in many other cars. The fuel tank stands up (rather than being under the trunk) and is directly behind that wall. Diesel+amp screws=fuel smell in trunk. Gas+amp screws=BOOM!

Rim care:
These wheels are PAINTED silver, they are not clear coated “aluminum rims” like on other cars. So treat them like you would the rest of the paint on your car — don’t spray or use anything on the rims you wouldn’t feel comfortable using on the hood! I have found a 1/2 bottle of full strength Simple Green and a brush will get off 90% of the dirt.

Spray GENEROUSLY on cold rims and brush. Spray again and wait 5-10mins, then hose off. If they don’t look significantly better at this point, nothing will help much and you’re better off repainting them.

Tire “bouncing” at highway speed:
You are driving down the road and feel a wheel “bouncing” off the ground back and forth. Steering shakes and it’s really scary. Slowing down makes it go away. The problem is 99% wheel balance. These cars are sensitive to wheel balance and will behave like this until the wheels are balance properly.

Get someone with a Hunter wheel balancer — there is a special model of Hunter that works REALLY well (someone tell me which one is best). Or try someplace that specializes in Porsche racing, high performance MB/BMW, etc, etc. Or try calling around to MB/BMW/Jag dealers to see if they have one.

What color diesel W126 should I buy?:
Here’s a tip I heard somewhere — “Buy a color your grand kids like because they’ll most likely be driving the car for a good portion of their life”.

Bulb out indicator is on, but all bulbs are working!?!?!:
Heck the two bulbs that light up your rear license plate. They are on the same circuit and will set off the indicator. You never notice them, but if they are burned out, the indicator will come on. Also check the taillights, as there are two tiny “marker lights” in the outboard corners of the car (ie. furthest away from the license plate). Look at both taillights when on and see if they look different (one has a light were the other doesn’t)

You cannot use the “bounce test” on these cars. Unless the shocks are completely blown out they will not bounce. But the ride will be gone long before that. Check the shocks for leaks, if they are leaking replace. Also 100k-150k is about all they are good for. Bilsteins are the best shocks to use.

1986 there was a major update, a face lift, then the engine alternatives 420 and 560 was presented.

  • 420 V8 4196cc  218hp (in Sweden)
  • 560 V8 5547cc 286hp (in Sweden)
  • 150kw 231hp and
  • 170kw 265hp
  • 200 kw 274hp cat.
  • 205 kw 286hp cat.
  • 220 kw 300hp without cat.

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