The other day I noticed the brake sensor was lighting up. Next thing I noticed was that the brake pedal was tight and the brakes
were staying on and getting hot. I took off two front wheels
and saw where the sensor on the right front brake had melted evidently because got so hot. The pads were fine. Also what was wierd was on the way home all of a sudden I had no brakes, the pedal would sometimes go to the floor, then the pedal would get tight again and brakes would stay on. They stay on all the time now and I can't drive it. Is this a caliper or MC problem or what?
Thanks, Phil
81 300D
260,000 miles

I have a similar, although not as serious problem. Brakes dragging. I hope someone can shed some light on this.

Frank.

__________________
'82 300SD

The following thread may have help you understand the problem. If both sides drag, it is likely the MC.

brake master cylinder

David

David,
I took a closer look at the brakes today. In fact I decided to drive it a couple blocks and see if it was both front brakes or not. Just after a short drive, I pulled over and could see smoke coming from the right front brake. So, it's definitely that front right caliper. I looked at it again, and sure enough it was froze. I forced the cylinder back in caliper, (was that a chore) but it did the same thing again, so must be shot.

Don't think an MC problem, but what puzzles me is why the brake pedal went to the floor a couple times when this first started as if bleeding the brakes. That seems MC related to me, unless the fluid was being forced up thru the top when i pressed on it. Anyway, called my local MB mechanic today, happens he has a used caliper in stock and I'm going to haul it in on the trailor in the morning. Will let him go over it, make sure there is no more involvement. $45 for the caliper and installation sounds pretty good to me.
Thanks, Phil

I think the brake was so hot (due to brake drag) that the brake fluid was boiling inside the system. You were compressing gas, not fluid. That was very dangerous. Remember to use Dot 4 brake fluid which has higher boiling point then Dot 3.

Replace the caliper and see. Let us know.

David

I have a question Phil. Did your benz pull to the right when the brake was dragging? I would think that should cause a significant pull to one side. I don't have any pull when mine drag, just wondering.

Frank.

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'82 300SD

Make sure you replace the brake hoses too! They are not expensive (even cheap oem) and are often the cause of dragging brakes. The fluid can get between the multiple layers and cause a blockage or restriction and still appear ok on the outside.

Bob D.

Frank -Good question, I failed to mention that, but yes, I noticed myself that it was odd that it did NOT pull to one side (right) as I would think. I could feel brake(s) dragging and holding the car back and that's all, no pull.

Bob -Thanks for the tip on the hoses. Will do.

Thanks,
Phil

David, Frank, anybody interested...

Turns out it was indeed the front right caliper causing the problem. Everything else fine. So, mech. put on the new (used) caliper, I drove it about 30 miles last night, she runs like a charm.
Phil

Thanks Phil. I'm going to get some new calipers for my car soon. I think they are the source of my problem as well. This just gives me that much more confidence in replacing them!

Frank.

__________________
'82 300SD

Phil,

Thank you for the update. Have you resolved the glow plug problem? If not, post a new subject for discussion. Everytime there is a problem, we all learn from it.

David

I think the service manuals recommend replacing both calipers on an axle at the same time.. that is, if you replace one front caliper, you have to replace both.

I replaced only the front left caliper on mine a couple of years ago. It was leaking fluid and at the time I wasn't comfortable rebuilding it myself, so I bought a rebuilt one. I didn't touch the right caliper (except to bleed 'em after the replacement) and have had no problems since then. I'm interested to see if the pads are wearing at the same rate. Well, not so interested that I'm going to spend an afternoon with the car jacked up just to look at the pads.. but interested a little bit.

- Nathan
'83 240D, 255k miles
'00 New Beetle TDI, 29k miles