Noise from new Brake

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  #1  
Old 06-28-09, 07:50 PM
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Location: Troy, Michigan
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Noise from new Brake

Hello, I have a 2004 Mercury Mountaineer with disc brakes in the rear. Recently (the last 2 months) my car has been shaking whenever when I braked. I found the source of the shake was from the rear rotors (surfaces were in very bad condition).

The last 2 days I spent hours to remove my rusty rear rotors and replaced with a pair of NAPA rotors ($34.99 each) and all new pads. After the work and I did a test drive and the shakes were all gone, but I now have a "once-per-rev" type of friction or light scraping noise. When I drove with window up, I could hear Shah-shah-shah-shah type of noise. With window down, I could tell the noise was from driver-side rear brake. When I drive along a long building (strip mall), the nosie reflected from the building was very loud.

Few things for you experts to consider:

1. During the hell process of removing the rotor, I bent the back plate somewhat. But I did bent it back so it looked almost normal, i.e., no visible point of scraping or interference.

2. When the left rotor was finally removed, I noticed the parking brake pads was kind of crooked -- both curving surfaces were partially pointing outward (i.e. in the direction of driver's left). I checked the anchors for the pads still looked ok, so without further correction of the pads I slip on the new rotor.

3. The caliper rocked a little bit even when the two anchor bolts were tightened. The amount of rocking reduced when I pumped out the piston onto the new pads. My guess was that was probably normal.

4. When I came back from the test drive, I jacked up both rear wheels and listened. I found the RIGHT wheel (passenger side) had a continuous friction noise seemly from the pads. I guess that's normal. The LEFT wheel has that type of friction noise for only about 180 deg of rotation, and then the noise built up for the next 90 deg of rotation and reached a climate, and then suddenly dropped silent for the next 90 deg, and then everything repeated in the next revolution.

So please help me out, for the brake noise I am now getting from the LEFT rear, is this a sign that the rotor (cheap chinese rotor) that is out-of-round, surface(s) poorly machined, or what have you? (I did have experience once from the past that a Murray's brake drum was horribly out of round.)

If the suspecion is on the rotor, what is the best approach to get the rotor replaced? Any advice on approaches? Just thinking about it give me some acids.

Shay
 
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Old 06-29-09, 03:43 AM
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Couple of things to check. Make extra sure the backing plate is not hitting anyplace. Did you clean hub before installing rotor? Dirt or rust under hub can make rotor not seat all the way. Check to see it anti rattle clips are in place.
 
  #3  
Old 06-30-09, 08:34 PM
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Pugsl, thanks for the pointer!

I ended up going back to take the rotor off once again. I found scratch mark on the backing plate. So I bent the plate back a little further and that solved the noise problem.

Shay
 
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