How should I troubleshoot drum brakes that squeal during forward travel, but not in reverse?

Question

I have an '09 Ford Ranger (about 100,000 miles) with disc brakes in the front and drum brakes in the rear. At least one of the drum brakes has been squealing during braking. Here are the facts:

• The squealing seems to occur during forward travel when the drum brakes engage gently. I can stop the squeal by using heavy braking (panic stop).
• The noise been getting worse over time, both in terms of volume and how consistently it occurs. It's been going on for a few months.
• Braking action seems to be fine. I haven't noticed degraded ability to stop.
• I had it in for maintenance as soon as I noticed the noise happening consistently and according to the mechanic the brakes are fine, they don't require service or replacement. (I'm not sure if I believe this)
• I have not noticed any noise while braking in reverse. However...
• I am very rarely in reverse. I almost always park in pull-throughs rather than spaces where reversing is necessary. Until now, I didn't know that drum brakes need to be in reverse to self-adjust, so I'll do some braking in reverse tomorrow and update this question with further information.

Assuming that attempting to force the brakes to self-adjust doesn't work, what else should I try in order to troubleshoot this squealing noise?

Answer 1

A very common cause of brake noise is dust buildup and vibrations. The noise can often be stopped or at least quieted by cleaning up the brake dust and applying a product called noise free to the back of the brake pads or shoes.

http://www.bavauto.com/fland.asp?part=nf4oz

I've found that this product works very well at eliminating brake noise when applied correctly. It is designed to eliminate the noise by dampening vibrations. Note that it is not intended or safe to apply to any components that cause friction to stop the car. (i.e. front of brake pads, rotors, back of shoes or drum)

Ultimately, the best way to diagnose the problem would be to get in there and take the brakes apart. If the shoes and the moving components all appear to be in working order, you can clean everything up and apply the noise free putty.

Answer 2

I had drum brakes on my Land Rover (8", 10" single and twin leading shoe), and what you can try is to chamfer the leading edge of the friction material - only needs 1/8" depth 60 degrees - so that the shoe does not "grab" on first contact. This worked for me many times.

Answer 3

My first level of effort would be to lightly sand the shoes with 80 or 100 grit, and remove dust from the drum area. If the inside (wear surface on drum) is glazed, hit that with the sand paper.

Intentionally, I have not addressed dragging shoes, broken springs, hydraulic leaks, bad bearings, etc.

Caution removing the dust as older shoes may contain asbestos, and all brake dust has small particles whose composition are unknown to you when you work around them.

Answer 4

Squealing brake shoes:

• Crystallized friction material, by braking abuse, leaks, bad material quality, overheating by shoe failure to retract correctly
• Brake fluid or oil leaks by failing seals
• Shoes have excessive play in their mountings

What I would do first?

• Carefully check the shoes for shiny/hard aspect (crystallized surface): rough up with 80 to 100 grits paper (cover your nose and mouth, that dust is evil :-) for your longs ) Also do some sanding to the drum's friction track, and clean everything to pristine conditions
• Check for leaks: any greasy smoke-black spot means a leak. Fix as appropriate, and clean the drum/shoes as well.
• Check if the shoes turns too much left or right, they should move but never turn (like when we correct steering when driving) If they do, check their mounting for worn out elements (they would be shiny metal).

For cleaning, I always used a rag impregnated with gas/petrol. Never use water.

If the shoes are badly crystallized, you need to change them.