Squealing brakes

  • 1.8L
  • 4 CYL
  • 2WD
  • 80,000 MILES
I have had squealing brakes since June 2015. My mechanic says rotors, calipers, and pads are good.
He said cleaning/lubing the brakes should fix the problem.
Last summer I would clean my rims with dollar store all purpose spray every week.
Would this be the cause of squealing brakes mixed with Montreal weather.
Do you
have the same problem?
Saturday, May 14th, 2016 AT 5:18 PM

1 Reply

Nope. There is things do-it-yourselfers and inexperienced mechanics can do to cause noises and vibrations, and there are things professionals do to reduce that chances of that occurring. If the squealing is occurring with original brake pads, it is usually due to the composition of the linings. More expensive and higher quality pads have a greater tendency to squeal, especially in warm, humid weather. Cheaper linings have less chance of making noise but they still have to exhibit the same coefficient of friction to maintain balanced front-to-rear braking. Because of that, it is rather impractical to try to make pads out of cheaper material.

If these are replacement pads that are making the noise, the most common cause is someone got grease or other contaminants on the friction surfaces of the pads or rotors. That does not hurt as long as it is washed off with brake parts cleaner before they go through their first warm-up cycle. If those parts get hot from normal braking, both the cast iron rotors and the linings are porous so the grease will soak in and never come out. The only cure for that is new pads and rotors and clean hands when the parts are assembled.

Another way to prevent squeals with new pads is to bevel the edges of the linings a little. That will stop the "fingernails-on-the-blackboard" screech. If that prevents the squeal during the break-in period, that usually lasts for the life of the pads. A lot of replacement pads come beveled already.

Speaking of break-in, your mechanic will take a test-drive and perform a half dozen pretty hard stops, then let the brakes cool down. If the customer is just allowed to take the car with no test-drive, the linings have not ground down yet to match the grooves in the rotors, so with less than full contact, the parts of the linings that are making contact build up heat real fast. That will melt the binders resulting in brake fade with a high, hard pedal. All of a sudden the car will just keep on going no matter how hard you push the brake pedal. The cure for that, assuming you survive, is to simply let the brakes cool down for an hour or two, then drive like normal. That only happens once and does not harm any parts other than the bumper!

There is a lot more that goes into preparing the parts besides simply hanging new parts on the car. That includes cleaning the points where the caliper contacts the backing plates of the pads, scrubbing the caliper's mounting surfaces, and lubricating all of those with special high-temperature brake grease. That's one step almost all do-it-yourselfers overlook. The pads are going to vibrate. The grease allows them to do that freely without transmitting that noise to other parts where it will be amplified. The aftermarket glues that claim to prevent that are totally ineffective. Properly-prepared parts won't squeal, then using those glues gives the false impression they are doing their job.
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Saturday, May 14th, 2016 AT 7:18 PM

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