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  #1  
Old 12-15-2003, 03:08 AM
unkl300d's Avatar
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Join Date: Jul 1999
Location: San Francisco, Ca
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Tech advice please-C280 brake noise..calipers?

Hello. I hope to have a tech give an opinion in order to get me to the next step.
Recently my low milaage 1995 C280 developed a 'dampened' brake pedal. The car seemed less efficiently braking and the pedal felt heavy when braking.

I had my indie change all four rotors and pads since the rear rotors were scored and the pads seemed close to ready for new.
The front rotors did have lip and the pads were at about 25-30%.

I figured that this would resolve the problem.
The road test after the new materials still resulted in a heavy pedal but it seemed to get better progressively. It did brake more efficiently , however.

The owner was not available at the time and the mechanic
in charge tested the vacuum of the master cylinder. It was OK.
I decided to observe as I used the car.

A couple of days later, the brake pedal seemed normal, braking efficiency was excellent but the pads squeaked terribley after the car was braking downhill.

Earlier the shop owner left a message for me stating that he was concerned that my calipers may be faulty since the heavy pedal was reported to him.

At no point in time before or after materials replacement did the brakes pull to either side and before the new pads, the brakes did not squeal at all.

The shop owner asserts by phone that the pad squeal is symptomatic of bad front calipers. He states that the pistons are not releasing back fast enough. He does not agree that it is just a matter of adding brake paste. He also tells me that he does not like rebuilding calipers because of failure rate etc.

My current observations after about 300 miles of usage is that
there still is no pull, car brakes well, pedal sensitivity seems normal but the pads still initiate squealing after braking downhill.
Once they heat up downhill, they begin to squeal alot and then even on flat road.

An exception occurs periodically in that the pads do not squeal
after downhill or flat surface but may develop later in the day.
So the squeal is inconsistant but does initiate 98% of the time.

Over the last two days I have heard a faint 1-2 seconds of sudued squeal pitch sound during normal driving without brakes applied. This has been a rare occurrance so far.

Question is, does this sound like a job for brake paste (no paste on pads right now) or does the caliper theory sound plausible?

If calipers are at fault can they be rebuilt with a kit reliabley by a mechanic?

Thank you.
__________________
1979 300D 199 K miles
1995 C280 95 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD
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  #2  
Old 12-15-2003, 08:05 AM
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Join Date: Jun 2002
Location: Cumming Ga.
Posts: 273
I think you should have the shop remove the pads and apply MB brake paste to the pads before replacing any other parts. Some slight brake squeak is not abnormal due to the high metal content of replacement pads. Also if they did not install genuine MB pads you may want to have them do that if the paste does not correct the problem. The part number on the MB paste is 001 989 47 51. Hope this helps, Robert.
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  #3  
Old 12-24-2003, 07:28 PM
unkl300d's Avatar
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Join Date: Jul 1999
Location: San Francisco, Ca
Posts: 2,267
update=for the archives

Thanks RPM55,
I purchesed the Mercedes brake paste. After removing the right side wheel I observed the brand new rotor had uneven wear marks! Concentric waves (ridges) and signs of glazing. I then got a second opinion and he diagnosed the same as the original mechanic, a slow retracting caliper.

So my original mechanic replaced the two calipers, brake hoses and at no charge replaced the rotors and pads (OEM).
He purged the brake fluid and restored it with 'Super Blue'.
After the break in period the brakes no longer make noise.

I thank you for your opinion, it helped me confirm my mechanic's
advice (his opinion was based on hearsay-read the preface).

This online help combined with physical observation is great help!!

__________________
1979 300D 199 K miles
1995 C280 95 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD
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  #4  
Old 12-24-2003, 10:00 PM
benzfan's Avatar
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Join Date: May 2001
Location: Toronto
Posts: 277
I had some serious noise problems with some aftermarket pads earlier this year on my 96 c280. My new OEM rotors seemed to be warped after a very short time with the aftermarket pads. Just for fun, I did some repeated stops from high speed and checked the rotors with a pyrometer. I repeated this about 20 times to try for some semblance of scientific method. I then switched pads to my old OEM ones and repeated the experiment. The old, worn OEM pads gave me rotor temperatures about 50 deg. C less than the aftremarket pads (front rotors - I didn't check rears), and didn't squeal. The aftermarket pads made a horrendous noise and had an extremely heavy pedal feel, as well as a pronounced fade when very hot. They didn't work worth a darn when cold either. There was only that middle ground when they were at their best. Clearly the aftermarket pads were not absorbing and dissipating any of the heat themselves but were leaving that job up to the rotors. The OEM rotors I guess were designed to work best with the OEM pads, and that's where I am today - new OEM rotors and pads. That being said, I had a set of Mintex pads and Stillen drilled rotors on my old 190e. They were absolutely without peer on that car.
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