Brake Question - PeachParts Mercedes-Benz Forum

psaboic · #1 06-19-2020, 10:01 PM

Hi folks,

Got a question regarding the brakes on my 83 300D. I have a pretty good idea of the answer, but I want to ask the collective experience here just the same.

Driving the car home this evening, it really didn't feel different, but when I got home after a 40 mile freeway drive I got out of the car and smelled something similar to hot rubber. As I walked by the left rear wheel I could feel heat coming off of it. I put my hand closer to the wheel and it was definitely hot.
Not hot enough to seriously burn you, but you definitely did not want to keep your hand on the wheel for any more than a couple seconds. The other three wheels were fine and cool to the touch.

What is causing it? I'm thinking stuck brake caliper. I replaced all the calipers on the car about three years ago but this one could be sticking I suppose. Anything else to consider/check when I pull the wheel off tomorrow (weather permitting). Any tips on the best way to check......I'm thinking visual and feel for dragging on the wheel.

Thanks in advance

Diesel911 · #2 06-20-2020, 12:07 AM

Quote:

Originally Posted by psaboic

Hi folks,

Got a question regarding the brakes on my 83 300D. I have a pretty good idea of the answer, but I want to ask the collective experience here just the same.

Driving the car home this evening, it really didn't feel different, but when I got home after a 40 mile freeway drive I got out of the car and smelled something similar to hot rubber. As I walked by the left rear wheel I could feel heat coming off of it. I put my hand closer to the wheel and it was definitely hot.
Not hot enough to seriously burn you, but you definitely did not want to keep your hand on the wheel for any more than a couple seconds. The other three wheels were fine and cool to the touch.

What is causing it? I'm thinking stuck brake caliper. I replaced all the calipers on the car about three years ago but this one could be sticking I suppose. Anything else to consider/check when I pull the wheel off tomorrow (weather permitting). Any tips on the best way to check......I'm thinking visual and feel for dragging on the wheel.

Thanks in advance

First suspect. Next is the Brake Hose.
Chock the Wheels, put it in neutral and jack up the offending Wheel. Start the Car and have someone step on the Brakes hard and shut off the Car and then rotate the wheel by hand and see if it dragging too much. Not a definitive test but if it is dragging you know that.

Check the end play on the Rear Hub. You are looking for rear bearing issues.

If it was a CV Joint issue one would think there would be noise.

dkr · #3 06-20-2020, 02:14 AM

It could be either the hose or the caliper. If you pull the wheel off, you should be able to see if the piston in the caliper will compress. If it does, it may be ok.

If your brake hoses are as old as the car, I would recommend replacing all of them. It is not a difficult job and you will need to bleed the system anyways.

The rubber can disintegrate from the inside and block the lines which can cause misdiagnosis of further problems as well as intermittent sorts of issues.

Quote:

If it was a CV Joint issue one would think there would be noise.

I think there would be noise and a missing/torn boot or a recent receipt for a Chinese axle installed.

Dkr.

t walgamuth · #4 06-20-2020, 07:29 AM

E brake also could be dragging.

psaboic · #5 06-20-2020, 11:00 AM

If I remember correctly, I replaced the rear hoses when I changed out the caliper about 3 years ago. The old caliper was locked up and the hose looked original. As for the E-brake, I haven't used that in a couple years, as the shoes needed replacing when I did the calipers a couple years ago and I never got around to it ( I know, I know.......)

Raining like an SOB here today (of course) so I will pull the wheel off and check it out as soon as I can. If there are any more suggestions, please feel free!! Thanks

psaboic · #6 06-20-2020, 02:50 PM

Ok, I managed to get the wheel off and look it over. It WAS the side with the caliper and hose I replaced about 3 years ago. I was surprised to find quite a bit of corrosion on the caliper, but what really surprised me was that the top pad guide pin had backed out about 1/3rd of the way. This let off some tension on the pad spring and let the pads get cocked in the caliper.

There was no lubrication left on the two guide pins, or the pad guide on the caliper. It either wore off, cooked off from the heat, or I forgot to lube it when I last worked on it (who knows, I am getting older)

After pulling the caliper off, the rotor (which looked surprisingly good) turned freely, so the E-brake is not dragging.

Sooo, based on the corrosion and the heat it was all exposed too, I am going to order a new caliper with hardware, new hose, and new rear pads. Guess the old girl is gonna be out of commission for a few days.

tyl604 · #7 06-20-2020, 08:31 PM

You must have ATE calipers. My Bendix calipers have cotter keys to prevent the pins from coming out. Not sure why you need to lubricate the pin; doesn't that defeat the purpose of the pin? Mine back out easily with a punch.

JHZR2 · #8 06-20-2020, 11:24 PM

Check how hot things got...

Unfortunately parts store rebuilds can be pretty lousy or have mismatched parts. On the rear it could be a parking brake too... Or a hose that collapsed, which acts like a check valve.

I had a front one seize up... And I had original hoses that were near bursting when I first bought the car. Brake hoses are only good for 6 years per DOT...