My friend has a 2006 300 with 26k miles. He has developed a squeaking noise when the front brakes are applied. I was going to apply some brake quiet to the back of the shims but found out that they are riveted to the pads.
I think from what I remember the noise began when we had to replace the front rotors as they were warped. Could it be the brake material is reacting with the rotors causing this issue? He does a lot of heavy braking so if he needs to get higher quality rotors, what should he get?
Depending on how the vehicle was driven, what your friend may be hearing could simply be the front disc wear indicators signaling that you have reached the end of the brake pad friction material. If so, they will need to be replaced. If you wait too long, the rotors will need replacement too.
I checked the pad thickness today and they were only about 1/4 used from what the new pads look like. He bought another set thinking that they were low too and when I was about to swap them out for him noticed that there was a lot left on the original ones.
There are a bunch of different chemicals to quiet different sources of squeaks in brakes. You might want to try CRC De-Sqeak. Also, of course, remember that disc brakes just plain squeak when they get dirty, and then stop again on their own...
Make sure the rotor shield (sheet metal behind the rotor) is not bent and rubbing against the rotor - that will make an intermittent squealing noise. I know this can happen on the LH cars - not sure about the 300. Usually it make the noise not just when the brakes are applied, but thought I'd mention it anyway - just in case...
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
Put a coat of brake grease or anti seize between the shims and the caliper on the outside and the shim and piston(s) on the inside. A light coat is sufficient.
Brembo makes very good stock replacement rotors, price is in line with NAPA (and other) premium brands.
The new rotors need to be cleaned very carefully, after they are degreased, you need to wash them with hot soapy water and wipe dry with paper towel until the towel doesn't pick up any more metal dust. This last part is very important.
Once reassembled, bed in the new brakes as recommended by the brake pad manufacturer.
In the old days (when you found disc brakes almost only on foreign sports cars) there was a lot more brake squeal. (We never did cure it on my friend's Fiat 124.) The back yard fix was to lightly sand the surface of the pads, just enough to remove any glazing they might have acquired. Then the leading edge of each pad was sanded to slightly bevel it, just enough to remove the sharp corner. It usually worked, at least for a while, and the best part was that the fix was free.
I know the pads for the LH cars have the trailing and leading edges totally chamfered (perhaps a lot of other cars too) - something on the order of, oh, 25 or 30° from parallel to the friction surface - maybe for that reason? Perhaps it helps shed water? Coincidentally that also has the effect of increasing friction surface area as the pad wears - maybe by 30% or more at end of life.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
I don't know if that could be the issue. I think it could be the rotor with the materials of the brake pads, since this started after we changed the rotors from stock to aftermarket ones. I may try putting back his old rotors and seeing if the squeak goes away. I know that you should put new pads in when swapping rotors but this is a trial for now.
The problem usually occurs after work of that type is done - the person doing the work inadvertently bends the shield - that's when the noise starts.
Well - it would certainly be worth *LOOKING* at the rotor shield as a preliminary to doing your experiment. If it is bent and rubbing the rotor, you could stop then rather than continuing with a possibly unnecessary experiment. If your engine doesn't start and you discover you're out of gas, do you pop the hood and start troubleshooting the ignition?
Not necessarily. When the bent rotor rubbing squeal problem occurs, it is almost always intermittent. Often it can be turned on and off by turning the steering wheel to one side or the other while rolling, and - yes - by applying or not applying brakes. Here's why: The squeal will happen when the right amount of pressure is on the shield against the rotor - too much pressure - no squeal; too little pressure - no squeal. Just the right amount of pressure - squeal.
The difference between the right amount of pressure and the wrong amount of pressure (to create the noise) is probably only a couple of thousandths of an inch of relative motion between the shield (mounted on the steering knuckle) and the rotor. The relative motion created by the stresses of turning and braking (as well as temperature changes) is more than enough to make the noise come and go.
Also - generally the noise occurs at lower speeds and not higher speeds. That is because the rubbing has to excite the resonant frequency of the shield.
My disclaimer is that I'm not saying for sure that this is your problem. I'm only saying that it should definitely be on the short list of things to consider and actually check.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
Sigh. I've been having that brake shield squeal with the right front wheel recently again. I've tried to work the junk (that builds up between shield and disk) loose without removing the wheel, but have not been successful. I was going to do it when I rotate my overdue tires, but at 60,000 miles and ten years of age, I think I will just buy new tires instead, although there is still some decent tread left.
Any suggestions for tires for my Intrepid? I'm partial to Michelin / BF Goodrich, mainly because Costco and BJ's have regular sales with them and they have an excellent reputation. The stock Goodyear Eagles have shown longevity though.
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