Brake squeal, what's causing it?
 

Hi, I have a 2005 ML350 with about 18,000 miles on it. Went in for service 3 months ago and they reported the brake pads had about 70% left over. Recently, the brakes have been squealing a little when coming to a slow stop. A couple of questions; first, what exactly causes these squeals? We've had snow all winter so could it be rust? The brake rotors look okay. Lastly, how to get rid of it?
Thanks.

Squealing has never been the problem on the 6 cyl ML's that it is on the V8's. Your squeal could be caused by all the salt dust that accumulates. I noticed that on my 02 ML500 that even after the problem was solved with the new pads that in the winter snowy season the squeal returned to a certain extent but went away after I had the car washed. I attributed that to the salt on the roads.FYI, my new 06 ML500 W164 has never squealed and the brakes appear to be of a different design.

what causes the squeal is the brake rotors get a glazed surface on them and the brake pads don't grab onto them so nicely when they are like this. You can apply the brake paste to the back side of the pads and then apply another substance called "Stop Squeal" by BG products that you apply to the face of the pads. After that, you can take some very coarse sand paper or a die-grinder with a pad like that and take the glaze off the rotor. If you do all of that, I guarantee there will no longer be any kind of squealing.

What causes it is either overuse of the brakes like when you are racing or just stomping on the brakes trying to overheat them or when you keep your foot on the brakes for a mile before coming to a stop every time.

Your prior advice is well taken but this last paragraph is not so true with the ML. First off, it's almost exclusively a ML500 problem. I'm not even sure the 430 has this problem. Secondly,mine started squealing the very first day I picked it up from the dealer - it was a December afternoon and the temps were low. Like all other cases with the 500, they continue to squeal during the cold months and are quiet during the warm months. My understanding is that the latest pads have practically cured this problem. I'll find out soon since I'm due to new pads in a couple of months.

Our 2001 ML430 has always done this when it's cold outside. I tried a different pad(don't remember which) which was quieter, but the wheels turned black in like 2 days. The last pads(Mintex) I used are cleaner, but noisier. Ours is a late '01, after the brake upgrade, so it has the 4 piston fixed calipers which I believe are the same on the W163 ML500.

This has occured with our ML320 numerous times. It only happened when it was cold outside. No snow required for the squeal.

Miraculously it's disappeared the last few months. We're using OEM brake pads btw.

Interesting - I never had the problem with my 02 320. You still have cold weather, don't you? You may actually have a different problem.

It's warmed up to around the 30s...

Well, the breaks used to be fine in cold weather before, so I don't know what's special about thise year.

Yeah right, and you call that warm. That's downright freezing as far as I'm concerned. Frankly, anything below 65 is cold. Anyway, at 30, my 500's will squeal.

The body may fall into hypothermia if the water temperature is below 70 degrees F. Even at 85 degrees it's possible. I still love the water though.

http://upload.wikimedia.org/wikipedi...e_You_Know.jpg

By the way, it lingers around the high single digits-low teens at nights. Still no squeal yet this winter. *Knock on wood*

I live in the North East and the brakes on the 2002 ML320 have never squealed. I have bought the car with 32k, now it has 65k, and I have to change the brakes.

I personally think the OEM Pad material is sensitive to cold temp. MB has a TSB to apply disk break quiet compound on the "Side" of pad to buffer the metal to metal contact between brake pad and caliper. but some of the folks that got that done at the dealer report that the compound didnt help.

My 2002 ML500 also has some brake squeel. It does not seem to be temperature related as it is still quite warm here. It seems to be related to a lot of city driving. It usually goes away after doing some highway towing.

There is a liquid made by BG products that is called Stop-Squeal. Basically when putting new brake pads on a vehicle, I always use this stuff and give it 2 or 3 coats on the face of each pad and between each coating I allow it to soak in and dry up. Doing this along with the brake paste on the back of the pad where it contacts the caliper, will give you a no squeal drive for a long time. However if the pads still have a good amount of life left to them and are squealing, you can rough up the surface of the pad with some rough sand paper (wear a mask and gloves because it will get dirty) especially if the pads are glazed over and then apply this Stop-Squeal and allow it to soak in a few times.

Do this and I can almost assure you that your brakes will not squeal. If they still do, there are still a few more tricks I know that will take care of it unless it is related to some damaged components.

One thing I recommend is to not drive with both feet and stop resting your foot on the brakes for the 1000 feet before you come to a complete stop.