Well, my brakes finally failed on my MB. As most know from other thread, my RR brake has been "sticking". It finally stopped, but I know my back brakes were very bad, but still had excellent stopping power.

I was told by some here that it was probably a swelled back brake line. While checking on another car I had in a shop, the mechanic looked under my MB and said it looked like those brake lines had recently been replaced and told that that if the brake pads were really worn out bad, that could be why they were sticking some, because they were compressing so low that they were not full going back out, but who knows.

Anyway, today I was driving the car home (I only drive it ONCE per week, which totals about 25 miles to keep it in good service). Brakes had been fine, but after driving 8 miles on a 4-lane without depressing the brakes, when I pressed them to make my turn, they were soft and went down much lower than normal. I was only about 2 miles from home at this point, but would have to use the brakes about 4 more times at turns. Braking power was still good, but when I pulled in the driveway, I depressed them a little harder and it feels as if only the front brakes are working now. I did not see any fluid leaking and the master cylinder is still full. Strange this happened suddenly (mushy brakes) and the fluid is still full. Could it just be where the rear brake pads are so badly worn? If new pads dont help, I will replace the hose as well, despite them looking fairly new. Are rear pad replacements on these fairly straight-forward and simple? Any special tools required?

Also, I went right after and bought new pads, but they are very small. I have not removed the wheel yet, but are the brake pads on these cars supposed to be so small? *Remember, I am used to driving big full-size 70s American cars with brake rotors as big around as a 13 inch tire.

Thanks.

No one has ever changed rear brake pads on a W126? Wow.

Yes, the rear pads are pretty small.
Can you get someone with some experience to help you with this brake job? You are not only taking you life in your hands, but also the lives of your passengers, the pedestrian, the people in the car in the intersection, etc.

Now, it could be something as simple as brake fade -- the dragging brake generates so much heat the brake fluid (and/or moisture in the fluid) boils and the vapor is compressible so the pedal gets soft. Or it could be a bad master cylinder. Or several other things. Changing the pads is easy, but your rotors may be shot and that is a little more involved.

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1987 W201 190D

Probable cause of the brake condition you describe is a master cylinder piston leak. The effect is to allow brake fluid to pass behind the piston thus losing the pressure differential between front and rear that is necessary for brake function.

You may want to get a master cylinder rebuild kit as well as your rear brake pads. Also, if you have never changed your brake fluid (should be done every two years) you may have condensate contamination of the fluid. Under the heat produced by heavy braking, moisture in the fluid can turn to steam which is compressible and can offer a similar effect.

what are you talking about? just replace the brake pads, yeah the rear pads are tiny compared to the front pads....if a caliper piston is locked and not retracting that could burn a pad real quick. Just be sure what is going on before you proceed with a repair. I doubt it's a swollen brake line..could be a locked caliper though...you'll find out quick enough when you try to retract the piston back into the caliper to make room for the new brake pad....good luck

Thanks. If its the master cylinder, I will shoot myself in the foot. I am having to spend out about $800 of of my hard earned savings to get one of my other cars serviced. I was not expecting another $101 for a master cylinder for this car, which is tiny and I dont think is worth $101.

I will get the brake pads replaced and see what happens.

FASTLANE Phil shows no master cylinder kits. My Bad. A new (rebuilt?) master cylinder is over $200.00. I guess I would just put new pads in also ... but ... do a good flush and refill of your brake fluid anyway. Could get lucky.

3 things:
rear pad is very easy. If you've done the front, you can do the rear. Knock out the pins, remove the retaining clip at the back of the pads, spread the calipers, remove the old pads and put in new ones.

letting the pads wear too much can damage the calipers

Running the car once per week 10 miles at a time doesn't really keep it in good shape. Probably does little more than put condensation in the oil. Drive it further.

You can get a W126 master cylinder for like $60 in the right places....

__________________
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Thanks... sounds simple enough. Well the RR was sticking, so I imagine that the pad is completely gone.

Sorry I was not clearer... I do mostly drive it once per week, but its a couple of trips out in that one day... sometimes two days a week with a couple of trips out each day. Until the brakes started sticking I was doing this.... after that, I was driving it at a minimal. I have four cars for different occasions and it seemed like the maintainence was piling up on all of them at once, overwhelming me.

I was not really planning on the MB needing anything for awhile until this brake issue reared its ugly head. I am hoping its only pads, but sure sure if I could get as luck for this to be the reason for my soft brake pedal and it now seeming like only the front brakes are getting pressure. Well see.


Thanks Pawo... I did see a MC listed at a local auto part store for like $60. One was $49, but it said w/o ABS. Strange, I thought by 1988, all Mercedes had ABS. Still I hope its not the MC. My "other" car has really drained my savings account. I had a fan bracket bearing go bad and it was like $170 for the part, $120 labor and $50 to have it towed to my mechanics. Its also due for engine mounts, tranny mount, valve cover gaskets and my MB also is needing tires and alignment.

Which way do the pins knock out? I cant figure it out. What holds them in place also?

Use a drift pin or a small diameter punch to knock the pins toward the center of the car. The pins rely on friction to keep them in place. Once you remove them you'll quickly understand how they function. Realize you need to completely retract the caliper pistons so the new brake pads will slip into the caliper. If you are at all unsure about how to replace the rear brake pads and ensure the RR caliper is functioning properly consider asking an experienced person for assistance.

__________________
Fred Hoelzle

Thanks, we got them out after I went out after I posted this

Well, we got the pins out just now with a nail - they came out easily... I just came in to now figure out how to get the calipers spread open. They seem locked???

Put one of the brake pads back in, put a C clamp on it and the back of the caliper. Use the C clamp to push the piston back. Or you can just put a screwdriver or the handle of a pair of pliers against the old brake pad and push. Harder but it works too. C clamp is easiest way to do it. The old brake pad protects the piston from damage.

Thanks... I was going to use that, but thought I would wait.

** While I was in here typing that, my dad was out there working on it and when I got out there he had got it loose and had already installed the new pads.

I placed the tire back on and what I did not know is that I had placed the pack of shims on the trunk lid and he did not know anything about them. Oh well.

There werent any shims on the old pads. We have to install the driver side rear tomorrow, so we will go ahead and install those and if the others rattle, I guess they will come back off. I am hoping this was the cause for my recently "soft" pedal and sticking rear brake.

Thanks for the replies.