Brake Noise After Pad and Rotor Replacement - PeachParts Mercedes-Benz Forum

shertex · #1 08-10-2006, 05:12 PM

Had front pads and rotors replaced. Noticed that, when braking with any degree of hardness, there's a cyclical sound (not a squeak, but I'm not sure how to describe it positively....maybe a thumping?) corresponding to the rotation of the wheel.

Called the tech, he said give and few days to settle in (??), then call him back.

Any idea what this is? OK to drive on? The tech will make it right....more of a pain than anything else.

Thanks.

softconsult · #2 08-10-2006, 07:46 PM

BS. Take it back and insist that they get it right. It won't get better on it's own.

Is this a dealer, and MB Shop or a general shop?

What brand of rotors were used. Ask them to be specific.
There are rotors made in third world countries.

What brand of pad? Specific answer required.
Did they use MB Brake Pad paste lightly on the backs of the pads?

It sure sounds like the rotors are warped.

Steve

catmandoo62 · #3 08-10-2006, 07:48 PM

usually you will get a pulsation thru the brake pedal if the rotors are warped.

dieseldiehard · #4 08-11-2006, 12:03 AM

Warped rotors usually caused by mechanics over torquing associated bolts. I agree take it back and make them fix it right.

SD Blue · #5 08-11-2006, 10:11 AM

Quote:

Originally Posted by dieseldiehard

Warped rotors usually caused by mechanics over torquing associated bolts....

Been there. There is a lot of frustration when all the money you have spent on getting the brakes fixed is nearly nixed by someone over-tightening the lug bolts.

tobybul · #6 08-11-2006, 12:13 PM

Sam, just curious why u think tightening lug bolts would warp rotors. The best way to tell if rotors are warped is when you brake there is a disntinct shake on the steering wheel or the car itself.

I have a similar symptom with my 85 300D (i'm referring to the sound - not the shake). The brakes were done in late 04 by a local german auto rpr shop. I only got the car this summer so I was not involved with the brake work. The previous owner is not mechanically astute so he probably did not detect what I am noticing now.

I hear a swish, swish, swish sound as the car is moving, more distinct at slower speeds.

Don't know what pads they used but am thinking that its also bearing related if not strictly bearing (which was supposedly repacked when they did the brake work.

I plan to go in there sometime (gotta order the bearing kit first) and take a look.

rrgrassi · #7 08-11-2006, 01:50 PM

Brakes do not take a few days to settle in. Take it back now and make them fix it right. The noises you describe can be caused by many things. Here are just a few:

1: Caliper not fully tightened, allowing excessive pad movement.
2: Brake pad dragging on rotor due to incomplete piston retraction after brake release.
3: Loose or missing hold down pins.
4: Loose or worn out wheel bearings.

grindMARC · #8 08-11-2006, 01:59 PM

Quote:

Originally Posted by tobybul

Sam, just curious why u think tightening lug bolts would warp rotors. The best way to tell if rotors are warped is when you brake there is a disntinct shake on the steering wheel or the car itself.

Rotor warp is a myth! What you feel in the pedal is the deposit left behind from a hot pad sitting on a hot rotor. There is a really, really interesting study on stoptech.com on the rotor warp myth.

Before taking it back to the shop, try bedding the brake pads. You're basically trying to make the pad surface mate to the rotor surface. You'll need a very quiet road for this. Take the car up to 60, slow down very slowly but don't stop. When you get to about 5 mph, take it back up to 60. This time, slow down a little more aggressively. Do it 3 more times. The last time you should be near 'threshold braking' (braking as hard as possible without kicking on ABS/lockup). You should drive for a few minutes in between each to let everything cool down a bit. Remember, don't come to a complete stop!

dieseldiehard · #9 08-11-2006, 07:25 PM

Quote:

Originally Posted by grindMARC

Rotor warp is a myth! What you feel in the pedal is the deposit left behind from a hot pad sitting on a hot rotor. There is a really, really interesting study on stoptech.com on the rotor warp myth.

Before taking it back to the shop, try bedding the brake pads. You're basically trying to make the pad surface mate to the rotor surface. You'll need a very quiet road for this. Take the car up to 60, slow down very slowly but don't stop. When you get to about 5 mph, take it back up to 60. This time, slow down a little more aggressively. Do it 3 more times. The last time you should be near 'threshold braking' (braking as hard as possible without kicking on ABS/lockup). You should drive for a few minutes in between each to let everything cool down a bit. Remember, don't come to a complete stop!

Rotor warp is a myth! = I totally DISAGREE!

I've seen too many rotors ruined from overtightened bolts, always caused by a mechanic that has an air tool set to max torque (or using a tool that doesn't have any torque settings!)
One shop here actually knows this well, they repair rotors that are screwed up thusly by turning them down.
I've sent people there who use a particular shop (which will remain unnamed) that ruins brand new rotors regularly. This is the only time I would recommend turning a rotor.
As for breaking in a set of pads, I usually do this when I have the inclination for the perfectionist that lies hidden, but I've done so many brakes without a Break-in that I've come to know its not mandatory on new rotors. On used rotors with grooves in them it is a good idea. But IMHO not usually associated with warped rotors.

SD Blue · #10 08-12-2006, 01:40 PM

Quote:

Originally Posted by tobybul

Sam, just curious why u think tightening lug bolts would warp rotors. .............

From my past experience and what they found, the lugs had been tightened very unevenly and the mechanic said it was probably from someone with an impact set extremely too high and running the first one down to full torque. Another factor they stated may have been heat. This was on a Ford 3/4tonHD pulling a fifth wheel trailer. (It is very nerve wracking to be pulling a load like that and when you have really lean on the brakes, they start to shudder.) All of this happened after having a new set of tires installed. (That series of vehicle has self-locking lugs.)

Maybe it was a combination of factors, but all they did was replace the front rotors and the brakes started operating smoothly again.