Benz-O-Rama

It was a nice day yesterday for my daily 45 minute drive home from work, so I decide slide the roof back and catch some fresh air. To my dismay I hear a high pitched squeal that varies with wheel speed but doesn't go away when I brake. At first I think it's brake pad wear indicators so I call my SA as I'm driving down the road. He informs me that my car doesn't have the old school type indicators that rub against your rotors and squeal when the pads are low, but rather a plastic sensor that will trip a warning on my MFD. The sound only goes away right before I stop and starts back up at about 15mph. Now here's the weird part. I get in the car to go to work this morning and the sound is completely gone.

When I took my car in for it's B+ service a month ago, my SA notified me that my front pads will need to be changed soon. I opted to wait until the MFD tells me that they need to be changed. I have not recieved any such message, yet.

Any ideas?

02S430

my pads squeal like hell had them checked and nuttin there fine, i even put the MB brake paste and it worked a little bit but now its back,

beanieBenz

I recently changed my front brake pads. I too was informed by my SA that the they were down to 10-15%. I noticed that the sensor embedded in the left front pad was already completely worn down and should have tripped the MFD long before the pads were worn down so much. I never received the message.

One of two things may have happened here... Either the little plastic sensor spike was broken off during installation or it malfunctioned.

In either case, I would pull off the wheels and have a look at the pad thickness. I have doubts about the reliability of the brake pad sensors.

konigstiger

Mention: P-B-42.10/51e FEB06 Front Brake Squealing / Grinding Noise. The squealing noise when the brakes are not applied is the result of the brake pad pressure retaining spring(s) slipping out of position and scraping on the face of the brake disc. The revised springs incorporate retainer tabs.

Benz-O-Rama

Thanks Konigs...

After I posted, I S'dTFF and found the same thing. I was just too lazy to search this morning. I'll make an appt and mention that DTB. I appreciate it.

SAguirre

This might not be the problem, but it is worth noting:

I personally change out my wheels twice a year when it is time to put the snow tires on and then go back to the summer tires. This last spring, after putting on my summer wheels and tires I noticed that I was getting some squeaking from my right front wheel. It happened when rolling and would go away if I turned to the left (I think). I was immediately thinking that it could be my wheel bearing since they had to remove the front right axel two days after I bought my car to change the o-ring coming out of the front differential. I was steaming!

I decided to remove the wheel and see what I could find. What I found was quite simple and surprising! Since Most German cars have lug bolts it is harder to mount the tire back on. Apparently, I barely bent the inside dust cover of the brake rotor with the rim when I was putting the tire back on. This cause the inside dust cover (or thin metal plate) to barely touch the outside of the rotor. I mean it was barely touching, but when the rotor got a bit hot, it would barely squeak. I bent the cover away from the rotor and the problem want away as quickly as it came.

BTW, I am at 22,000 miles and have about 85% of my pads left. I guess I don't use the brakes much.

They do say in German that cars are a Fahrzeug (a driving thing/stuff) not a Bremszeug (a braking thing/stuff). Just a stupid German joke for those who always got good life out of their brakes.

Steve

Benz-O-Rama

Hmmmmmm,

Very interesting. As I do have aftermarket wheels on and the sound does seem to be coming from the right front. And it doesn't make the sound in the morning when I leave to go to work, when the rotors are cool. I've only really checked when I was about 15 minutes into my drive home from work when they've had ample time to heat up. The car is going in tomorrow and I'll tell them to look at that as well.

Thanks.

jangy

That is really common with us do it yourselfers. The clearance between that dust plate and the rotor is MINIMAL at best. It is very easy to adjust and may be source of your noise. Usually, they get loose and start to rattle with idle changes, but anything can happen.

Benz-O-Rama

I dropped it off today. The dealership is less than a mile from my work so it's a peice of cake to drop off and pick up. But they gave me an ML350 that smells like smoke

Benz-O-Rama

Got the car back today. Dealer said that my front rotors have devoloped a lip and that when the rotor gets hot, the right/front is expanding just enough to rub against the pad at this lip. Of course they're recommending new front rotors and pads. I have 15% front pad left, so when it's time for those to be changed, I'll bring them my own rotors and have them put them on. Or I may get froggy and just do the whole friggin thing myself.

They said that the backing plate spring was in perfect position. I'm also gonna pop a wheel off and look at that dust cap.