My 1994 E420 has been plagued with the most unbelievable brake squeal problem. My mechanic recently replaced the front pads and rotors. Prior to the replacement, there was no brake noise to speak of. Shortly thereafter, I began to have squeal problems. The squeal is only a problem under light brake pedal pressure, and at low speeds, just before coming to a complete stop. However, about 40% of the time, just before coming to a complete stop, it seems to me that the ABS system comes on, and I feel a shudder in the brake pedal, I hear that thumping sound, and the car almost lurches forward a little as the clamping pressure seems to release somewhat. This occurs even though my pedal pressure does not vary.

The mechanic has already tried putting factory pads on, but if anything, the problem is getting worse every day. I made sure that he used the blue Mercedes paste on the back of the pads. Other than the pads and rotors, what else could be causing this problem? I am most distressed about the strange ABS behavior at extremely low speeds. Thankfully, when braking in any other circumstances, the brakes perform flawlessly. However, driving home in bumper to bumper traffic is literally unbearable due to the noise.

I am due back to the mechanic in a couple of days, and would love to have some suggestions before then. Thanks a lot in advance!

Be SURE that the rotors were FACTORY as well. I have had the cheaper rotors give me HELL on squeaks. I will never install them again. We use ONLY OE PADS AND ROTORS. The new paste is silver in color and can be ordered from the dealer or from us.

__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

The really off-putting thing now is the strange ABS behavior. As I was coming home in bumper to bumper traffic, I eased in behind the car in front of me, the ABS engaged, and I lost braking power for a split second. I had to get off the brake pedal completely and then slam down my foot to keep from hitting him. Could non-factory rotors cause this to occur? I am really puzzled.

Maybe one of your calipers is seized and only one front wheel is braking. Have someone watch each front wheel while you brake. If only one locks up and then starts turning when the ABS engages, the one that never locked up probably has a seized caliper. As such, you would be trying to stop a big ole Merecedes with only one front brake working. Worse yet, if it is seized, it may have happened with the pads pressing firmly against the rotor. That would ruin the rotor, and the pads. Severe over heating should be pretty obvious with a visual inspection.

Anyone else agree with this possible theory???

As long as I don't have a warped rotor, and know that the pads are new and there is no metal to metal contact, my solution is to turn up the volume on the radio.

My $0.02,

With all due respect, unless I turned up the radio to the point that it blew out my eardrums, nothing would drown this out. You can literally hear me coming from over 150 yards away! This is not your normal squeal. That, coupled with the bizarre ABS sensation, leads me to believe that the caliper or some other brake component which is causing the problem.

I'd bet that the aftermarket rotors are the problem. As Donnie said, OEM parts generally are the least trouble prone solution. If your ABS is getting whacky, then something was done to disturb the sensors. The hubs are still original, right??. Are your stops (such as they are) in a straight line, or are you pulling? This is not something to mess with, Your brakes are the only thing between you and other objects (cars, people, buildings, etc.) Get it squared away pronto...PLEASE..

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.

Amen to that brother! My wife and kids are in the car sometimes too. I plan on taking it back to the mechanic on Monday to have this sorted out. Per Benzmac in an e-mail, the squeal itself, if severe enough, can set the ABS sensors off. I just have to believe that the rotors are causing the problem, and not the other way around. I just don't think that the sensors could create the squealing racket I have been putting up with. Could extended faults caused by the squealing adversely affect the sensors themselves? Do the sensors have a typical life expectancy that has been shortened due to this squealing? I plan on having the mechanic make sure the ABS sensors check out per spec before I accept the car as fixed.

Thank you everyone for the help. If anyone can answer those last two questions, I would greatly appreciate it.

The sensors are Hall effect devices. They do not directly contact the wheel components. The vibrations set up by the squealing brakes may produce ABS oddities. Also, if they are not properly positioned, they will give incorrect information to the ABS computer. I hope they didn't pry on them whilst trying to get the rotors off. Beware...

__________________
Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.

My long brake squeal nightmare is apparently over. Although the mechanic insists that he used factory pads, today he replaced both the pads and rotors, this time using "Power" rotors which are slotted for better heat dissapation. I feel that whatever rotors he used last time were the culprit, as this is the third set of pads in the last 6 weeks, and the first time the brakes have been silent. Thanks to all for their advice! By the way, are these slotted rotors any good? I figure that the slots will eventually disappear as the rest of the rotor wears, at which point it will pretty much be a regular rotor again.