meowy84

So I've put about 4,000 trouble-free miles on my '84 500SEL (odometer now reads somewhere arouns 185,000 miles) and I've got a few questions.

Since no mechanical thing is perfect what are the weak areas of these cars? Any mechanical pieces that give more trouble than others? Obviously proper maintenance is imperative and after 100,000 miles some attention should be given to the chain but other than that what should I watch for? Do the alternators or water pumps or the fuel injection distributor pumps (I'm referring to the cast box on the drivers side that contains the fuel distribution system) fail? Suspension faults? Etc?

Hattaresguy

Chains every 100k thats about it. The M117's do seem to wear their cams though. MB makes a pretty bullit proof engine, other then that jsut the usual W126 problem areas.

meowy84

And what are these other "usual 125 problem areas"? I'm looking for everything that's known to be a problem area whether it be chassis, suspension, electrical, exhaust, etc etc......? Anything and everything...

Which models are the M117?

w123_w126

The M117 is the 5.0 and 5.6 L engines. You have an M117 in your 84 500.

These are not necessarily unique to the w126 but at your miles some things to consider:

Glass delamination

Rust under the rear window

Worn rear window seal resulting in water in the trunk

Flex discs

Rear axle shackle

Axle shaft

Rear wheel-bearing

Drive line bearing and support

Propeller shaft boot

Drive line support and bushing

Exhaust hangers

Exhaust system

Engine mounts and shocks

Subframe bushings

Tie rods and ball joints in front

meowy84

Oh dear, I'm already getting some of those things. *sigh* In particular I am experiencing glass delamination in the rear glass in the bottom corners. Things such as exhaust system and hangers and rear window seals I'd consider usual wear and tear items for a car of this age.

What is the rear axle shackle? Are you referring to the rear disc brake supports (the sort of X-shaped braces that are screwed together to which the caliper attaches to) and the rubber bushings that these are connected to via the rear suspension arms (sorry for the bad explanation)? I do get a slight banging noise in the back when I go over heavy bumps that sounds like a loose exhaust hitting the underneath of the car (but of course it isn't the exhaust in my case). I suspect a deteriorated rubber suspension bushing somewhere in the rear.

As for the axle shaft you mean the rear axle drive shafts and if so is it the CV joing that goes on them?

So far so good with the rear wheel and drive line bearings. I've had bearings go out before so I know the initial low humming noise to listen to.....but...what is involved in their replacement? Is it a home-garage kind of a job or is a heavy hydraulic press involved to press the bearings out and some specialized tools to disassemble the rear suspension system?

rickyfanmdr

I had a 1985 380SE for 17 years and 105,000 miles. The transmission is the biggest weak point. I went through 2 replacements in 100,000 miles.

w123_w126

The shackle and the axle shaft are part of the axle assembly prone to wear – common symptoms are a click or popping sound when the rear wheel(s) are turned while on a lift or the axle shaft has excessive lateral motion.

meowy84

rickyfanmdr, what were the problems with your trannies? I always thought that the MB trannies were pretty good. I was told by an old mechanic that works only on European cars that the only major problem with older high mileage MB trannies was hard/harsh shifting. Indeed this is something I'm experiencing myself but once the trans shifts there is no slip or any other problems in any gears. I do however get a slight delay in the 1-2 upshift. There's about a 1/2-3/4 of a second where the engine seems to freewheel before the 2nd gear engages.

meowy84

rickyfanmdr, I forgot to mention that I suspect that my shift delay is probably an adjustment issue with the linkage maybe or a computer issue rather than a mechanical problem with the trans itself. Of course that's only a guess on my part.

W123_W126, for this slicking test should both back wheels be in the air or is the one you're testing enough? Also how much lateral play is abnormal and won't having the rear suspension unloaded give a false reading in any way? To test for this clicking should I have the trans in neutral and therefore the driveline unloaded or in park and have the differential do the work? Also to test for the lateral movement is it enough grab the wheel as though you're going to be checking of loose balljoints by hand and so instead of rocking the wheel pull it toward and push away from you?

meowy84

slicking=clicking

w123_w126

This would be up on a lift – some movement is needed but this would be noticeable, yes, it’s basically a good grab and pull – an experienced MB tech can tell. Yes, the tranny is in neutral with the wheel turn test. There should not be any noticeable resistance or noise when the rear wheel is turned on a lift.

rickyfanmdr

I think everyone experiences the hard/harsh shifting. As far as I know, that is just part of the car. I can't tell you very technically what was wrong with my transmissions. The first one would stick in first gear, and I tried several repairs and replaced it when I got stranded and towed a couple of times. That happened at about 60,000 miles. The second one made a weird sound and I was able to nurse it into my mechanic's shop, which was only less than a mile away. That was at 100,000 miles.

Hattaresguy

Don't forget rust, I was able to put my finger through the frame rail on my 420SEL parts car. Also the ABS acts up once in awhile. And how could it be an old MB without vacuum leaks, cruise control, and AC problems? Lets not forget the front ends usually need to be rebuilt between 200k-250k. Also the trans are strong but again 200k-250k is about all they are good for. Although some last much, much longer.

W126's are nice cars but they are getting up their in age. They will all need work to keep them going. I sudjest becoming a diy type person if you want to own an old MB. Or find a good indy and don't be afraid to drop a few grand a year.

meowy84

rickyfanmdr, by sticking in first gear you mean it wouldn't want to shift out of 1st into 2nd? (I read on here that some MB's started out in 2nd gear.....?) Wow, two trannies at those intervals...That just shouldn't happen on a car as pricey as this. It always bothers me that the expensive luxury cars seem to be less reliable than the run of the mill machinery. I realize that their complexity has something to do with it but still after paying as much as these cars cost you shouldn't experience many problems for a long, long time.

Hattaresguy, I get that annoying ABS thingie as well It seems to come on rather randomly. Sometimes it's on as soon as I fire up the engine in the morning and sometimes it comes on after several miles of driving and at other times it comes on only after I shut the engine off and turn it back on again (as at a gas station) and other times it doesn't come on at all.

farooq

yeah that ABS thing is pretty annoying.. it simply means worn out sensors most of the time.. my ABS works perfect still i have my light on and off randomly.. from my experice these aging cars can show many different problems depending on how well kept they were....

Hattaresguy

Pull and clean your ABS sensors. The front ones are simple to clean, but I am not sure where the rear sensors are.

meowy84

I've seen the 2 wires and connectors on each caliper. Are there 2 ABS sensors for each caliper? Also how do you remove and clean them? The repair manual that I have access to doesn't cover that part.

donbryce

Don't confuse the ABS sensor with the brake pad wear indicators. The sensor is about the size of an AA battery, and mounts with a bolt to the rear of the backing plate area. The sensors are 1 small wire/pad, which you can see on the caliper, and join in a larger lead. The rear ABS sensor (1) is near the driveshaft at the differential.
As far as the ABS is concerned, my dash light comes on at random times, but my driving habits with my 126 never see me in ice or snow (off road from Dec until April), and I've yet to recall getting caught in a rain heavy enough to make the ABS very useful either. For the $$ and trouble (I did clean them - no effect), I just pulled the dash cluster out and pulled the bulb socket out far enough so the light isn't that annoying. (I'm told don't remove the bulb, however, not sure why, something about a 'working' ABS requires it to be intact).

farooq

i stuck a piece of black tape over it :p

btw..how to pull out the dash cluster??

braverichard

You have to insert a tool in between the cluster and the "wall" that holds it to the dash. Several people use a hanger and make a tool that will go in there and unhook the cluster then pull it out.

Check out the very top part of this page: http://boostnbenz.1baddsm.com/DIY/GaugePaint/

farooq

common weak points of W126 - V8

Hydromat Suspension - if not maintained well of the car was driven carelessly on pot holes, the hydromat setup will tend to fail frequently.. common problem is the bursting of membrane in accumulator causing the vehicle to sag

AC commpressor - clutch may seize up during long term sudden inactivity of compressor after heavy use.. such as when the season changes from summer to winter.. to aviod this.. run AC for 15 minutes atleast every week

On dash clock - likes to change time zones on its own.. well actually it quits working properly on these old cars..

have ur wood trim polished regularly at some wood workshop or else it wont look good...

gauge needle colour fades.. repaint them..

the lines for center locks may start leaking by hardening and cracking over time.. replace lines.

ATF cooler - fan less ATF cooler has near zero effect when snailing in town traffic congestion. Easy fix this with an after market fan, mounting kit, thermostant and required wiring. Install fan in pull configuration

Radiator - develops leaks over time.. faster if u are not using Mercedes geniune coolant which is too expensive..to continue using after market coolant.. upgrade to a high flow high efficiency after market radiator..copper tubing and aluminum fins design with fin density of 12 - 15 per inch is suited best for the given size.. contanary to common belief.. using even higher fin density will not improve cooling efficiency but rather restrict air flow.. unless u replace the engine fan with higher blade angle.. and there is not enough clearance to do so.. also consider noise..

iawegian

This was one of the better run-down's of the cars. Thanks to all who posted.
I've been getting into the 126 chassis because of the diesel availability, and conversion to burn WVO.
Sagging rear, touchy cruise control, and loss of vacuum shut-off has been a hallmark of mine. Fortunately, PerformanceProducts4Benz.com has some good stuff. I love their exploded parts diagrams.
Keep this stuff alive! DIY's can keep this planet green!

harkgar

Faithfully?

Did you drive you car on the track?

If you did not do any of the above 2 then whoever owned it before you did.

There is absolutely nothing wrong with my transmission (1985 560 SEL) and I stick to the service schedules and use nothing but the best fluids recommended by MB. I do give the car the best tender loving care.

DslBnz

Most of the items mentioned on this thread all pertain to the age of the vehicle. Not really "weaknesses". All parts in motion, and those exposed to the elements will age and need remedy on any car. Once they are fixed, they are fixed for another 20 or so years if done right.

It is really important to become a DIY'er because most people that work on these cars have limited experience and their priorities are not for the best interests of the customer. Only YOU can care for YOUR car the way YOU want it to be cared for. These cars are not daunting to work on, these cars were designed to last forever, and to be rebuilt and remain in service for as long as you can afford.

In regards to transmissions. I have 3 Mercedes-Benz S-Class vehicles (W126 only). Two have about 290K miles each and one has 150K. They all have their ORIGINAL transmissions, and they never flare or shift overly harsh in any condition. They need to be serviced every 30K miles with fluid and filter RIGHT ON SCHEDULE, or they will not take kindly to it.

harkgar

Check this one out guys: http://www.s-klasse-club.de/gb/index.html

It is an excellent site.