Squeeking ML 500 brakes?!

[JonH]

Can anyone shed any light on this problem...
My '53 plate ML 500 has developed an awful squeeling noise when braking at slow speed - it got so bad I had it in today to have new pads fitted even though they were not needed yet in case it may solve the problem but the noise has got worse!

Help??

 

[television]

If the pads were fitted correctly with the correct grease then I do not know why, is it something else,but what

 

[Uncle Benz]

Most likely the discs. Have they got a lip at the outer edge?? It is like a damp finger on a wine glass when you brake, if they have. New discs will cure your problem.

 

[JonH]

Possibilities...

Had a chat with someone last night who reckons the discs, although relatively little worn, could be "glassed" - a heavy car with constant brake use with auto box and often short journeys can glaze the metal surface.
The problem is only there when braking at slow speeds and this sounds like rubbing on glass so may not be such a strange idea?
Apparently the discs need roughing over and correct grease applying to bed in, then gentle use for first few miles.
Getting done today so will note progress...

 

[BlackC55]

May I suggest shamfering the edges of the pads.

What pads were used?

 

[wireman]

Glaze bust the working surface of the disk(s), use medium sand paper and make them look dull. glass paper is my prefered abrasive for this job since the redual abrasive bits which will be left behind break up into very fine harmless dust and will not cause damage to the disk or pad in service, silicon carbide and aluminium oxide (emery) will not break up and can cause uneven disk face wear or even a groove.

If the outer edge of the disk has a lip that stands proud of the working surface you might try to remove it with a file or sanding disk taking great care not to damage the working face. Dont forget the disk has two sides!
It is well worth discarding the disks if the wear is of any depth.

Putting a small chamfer at the inner and outer edges of the pads can help but the efficacy of this will degrade as the pad wears. Chamfering the leading edge can also help, on some cars this is standard, the pad has a full depth 45deg slice off the leading face/edge.

Frequent light braking is a common cause of glazing, the brakes can get very hot in a quite short distance if you subject them to continuous light duty. Try to avoid traveling along with very light pressure applied to the service brake, instead reduce your speed (with the brakes of course) and let the brakes have a rest untill you need to shed some speed again.
Giving the brakes a good hard push at moderate speed every now and again will clear the working faces of tired material (a powder with the properties of a fine metal polish crushed into the pad faces) helping to keep them in good order and reduce their tendency to glaze.
Glazing is less of a problem with modern asbestos free kit than it was in days of yore.