I replaced my rear pads and rotors last Saturday following housecor's excellent write-up on www.shiftice.com. The replacement went fairly smoothly thanks to all the great info, but I'm now hearing some intermittent noise coming from my rear brakes. It sounds like a scraping/grinding that seems to occur randomly. It never happens when I'm actually braking and it doesn't occur all that often.

This is the first time I've ever replaced anything brake related so I'm worried I did something wrong/screwed something up. Is it common to have this type of noise for a little while after a replacement? Any ideas?

I used Hawk HPS pads and Brembo rotors and went through the bedding process. Thanks in advance!

EDIT: 2002 GLE

 

Well damn, just found this related thread here on the org. When I removed the calipers the dust boots were in good shape, but when I starting rotating/compressing the pistons the dust boots would also turn and sort of twist up around the piston. Didn't seem like there was any way around that happening. I tried untwisting them as much as possible but couldn't get them back to they way they looked before I started.

So is it safe to say that I jacked my calipers or that they were bad before I started? Car only has 85k miles on it, but I guess if this is a common problem it could happen whenever. Is getting new calipers the fix here?

 

This happens to people all the time. The best practice for any caliper boot is to spend the time and clean it well. Follow that up with a light grease on the boots to ensure they are protected properly from the elements. Specifically on the rear calipers, it pays to gently loosen it from the piston. After all this done, then begin returning the piston to its beginning position.
In your case, you can always try to get back in there and work the boot loose from the piston. Make sure to be careful not to puncture the boot. It's worth a try.

 

I don't really know much about cars but I like to tinker which, more often than not, gets me in trouble . Exhibit A - my current grinding brakes. So forgive the ignorance of the next few questions...

1.) What's the point of the boot in the first place?

2.) Why is a twisted boot a bad thing? Does it keep the piston from rotating any further, locking it in it's current position?

3.) What exactly causes the grinding noise? The brakes feel like they work as they should and I don't have any grooves or cuts in my rotors (although, I haven't driven the car much since I replaced them). Is continuing to drive the car without addressing the issue a bad thing?

 

At some point or another, everyone gets themselves into trouble.

1. The purpose of the boot is basically to keep debris from damaging the piston seal. The piston seal prevents air from entering the hydraulic system and hydraulic fluid from exiting the system.
2. Twisting a boot, especially an old one, can cause it to rip or tear. Reference #1. It can also inhibit the piston from turning effectively. However, if a twisted boot prohibits the piston from resetting when servicing properly, it's probably time for a new caliper or a rebuild kit.
3. The grinding noise can have a myriad of causes. The first place I would check? The brake shield. It is thin sheet metal and is often accidentally bent into a position that makes contact with the rotor.

When it comes to brakes, improper operation is a safety issue. It's a PITA, but I would double check everything sooner rather than later.

Good luck!

 

Thanks for all the info, I appreciate you taking the time. Unfortunately it seems I've misplaced my wheel lock. S.O.B. Guess I'm taking it somewhere. I thought by doing the work myself I'd save some money and gain some experience with brakes. I'm 1 for 2 I guess. Thanks again.

 

You know, having driven the car a little bit more and giving a better listen to the noise I'm starting to wonder if it's a wheel bearing issue and not the brakes. The noise occurs at slow speeds and I've heard it at up to about 40mph. It's intermittent and it DOES occur while I'm braking. If it was a seized caliper it seems like the noise would be constant. What's the best procedure to diagnose a bad wheel bearing? Can you tell if a wheel bearing is bad with a visual inspection?

Since I bought the car I've had to replace both front wheel bearings but haven't replaced the rears. The noise sounds very similar to what I was hearing when the front bearings went bad. Maybe I hit a bad coincidence and replaced the brakes right when a bearing went bad or maybe the way I jacked up the car (one side at a time) caused one or both to crap out. Is that even possible?

I'll try and take a video of the noise and post later tonight.

 

There's a certain value in being able to find the humor in a seemingly bad situation and I just found the humor in my brake noise problem. Driving around today I pinpointed that the noise was only coming from the driver's side. I got home from work, jacked the car up, and removed the wheel only to find the coat hanger I used to hang the caliper from still dangling in my wheel well . DOH!!! Removed the coat hanger and the noise magically disappeared. Pretty sure I'll never make that mistake again .

I'm just glad I didn't take the car to Midas or some other shop and have them remove the wheel and tell me I left a coat hanger in there. I was so close to taking it in.