My personal experience is that most brake squeal does NOT come from the contact between the pad and rotor but from everywhere else.....like the back and side edges of the pads (and pad "springs" or "retaining clips") and other sliding/rubbing METAL to METAL parts, including the back of the pad to the caliper piston. For me, if I remove the pads after several hundred miles and look very carefully, you will see where there is metal to metal contact. Use the appropriate lubricant (for high temp AND PRESSURE, like certain moly lubricants). Also lube any cliper bolts where there is sliding. Needless to say, be very careful where you put grease.

I recall a tech bulletin for the ML showing putting this lubricant on the METAL EDGE of the pad which may be posted somewhere in this forum.

Good luck.

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Jim

The squeal when you back up, is it first thing in the morning or when you take the truck out after sitting overnight? If so, it is probably only a coincidence that it is when you back up, and is caused by mild surface rust on the rotors. It is from the truck sitting, condensation forms, and hazes over the rotors. Once you get past the first stopping, the rust is cleared off, and they operate normally (I assume). If you parked the truck overnight where you would pull out forwards, it would probably happen then too.

The only thing you could try is giving the rotors / calipers / pads a good blast with brake cleaner, to clear off any dust build up. I use ceramic pads up front and they work great and are VERY quite.

The squeal happens everytime I back up. I'll have to pull the pads out to see if there is any metal to metal contact. I've lubed the edges and tried different types of squeal treatments. It might be comming from a clip or something else. It just seems odd it only happens when backing.

Update: Took the brakes apart again. This time I lubed the pads at all contact points (not pad to rotor). Plus double shimed pads. Squeal is gone.

Well, if the squeal comes back, you could try the pad to rotor contact point lubrication technique. But, there is a distinct possibility that braking distance could be adversely affected (but I bet the squeak would go away, but would probably be replaced with a loud "thump" and sudden stop)!

Yep that's true. Lets hope the squeal doesn't come back. Or I maybe forced to try that technique.

sorry to chime in so late on this. I worked on several MLs with squeeling problems. The owner and shop manager had me try several things, nothing which helped the problem for more than a week or so. MY OWN findings showed that the #1 thing which affects the squeeling is to properly bed in the brakes. If you try to bed them like a car it is NOT enough, as they are rather large truck-ish brakes and do not warm up fast like a car brake, even BIG car brakes such as on a AMG. You need to really really do a number of very very hard brakes maybe about 20. You can do 2 in sequence, then wait 30 seconds, do 2 more, etc, til you KNOW the brakes are hot. If you can't SMELL them they are probably not hot enough and not bedded well enough. This may sound like BS, but this really gave good lasting results. Of course when assembling yes you want to use the greasey assembly paste like MB wants you to use, as normal, but just use the normal stuff and in normal quantities, and don't use the gooey plasticy stuff, you want just the normal high-temp grease stuff, you can even use high temp bearing grease actually. Put it on the parts of the caliper that contact the back of the pads, and the parts of the pad that slide on the caliper (or on the part of the caliper where the pads contact on the edge, either way is fine, no need to do both). A really good hard bedding in always made the complaint go away. If they are squeeling, then in my opinion it's too late. If the rotors are/were new, give a good non-directional finish again (scotchbrite rotary pad on a die grinder is good enough, and replace/start over with the pads).
Gilly

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