Problem with the wife's Daily Driver...

[newyorkin]

Hey all...

Our 99 Pontiac Montana has had a "thump" when rolling since we bought it. It's now a 1.3 years and 10,000 miles later, and I finally replaced the suspected bearing, and the thump is gone...
About a year ago, I had a shop change the drivers side axle because it looked a little off center and we thought that was the thump. That wasn't the thump, but after the guy touched it, there was a grinding noise in hard/warmed up braking. It sounds EXACTLY like worn to metal pads.
I tacked it on to whatever was causing the thumping, the bearing, figured it wasn't the brakes because the pads and rotors were brand new (replaced while trying to find the thump).
After swapping out the bearing yesterday, the grinding is still there.

It only occurs when warmed up and late/hard braking. The rotors are smooth as a baby's butt. The pads have a lot of meat on them. Everything is tight, caliper/bracket/wheel, everything appears to have clearance.

It doesn't seem to stop any differently either. It's hard to separate feeling from noise when it occurs, but it seems to still brake very smoothly, not like it would if there were some kind of brake interference.

The rotors do have sort of a cut in them, the top and bottom edge of the braking surface have a higher edge, like the pads have worn the rotor down perfectly. Nothing looks like it should grind, though, all the contacting surfaces are perfectly smooth.

Anyone have any ideas?

 

[4X4HIGH]

Your description about the rotor tells me that you probably have a very HARD set of pads on there that have worn the rotor pretty badly. I know exactly what you're describing about the rotor. I'll bet if you machine the rotors (if they still can be done) and change the pads your problem will be gone.

 

[sled_dog]

notice caliper to rotor clearances? I put new rotors and calipers on my 97 C2500, couldn't locate a grinding noise(sounded just like metal to metal pads, but pads were brand new). Finally I realized the caliper was rubbing the outside edge of the rotors(yay for aftermarket parts from Advanced Auto). Could more miles and the sound went away(makes me think it might not be your issue).

What kind of pads were installed? The fact that they've worn good ridges into the rotors after what you said 10,000 miles? makes me think they are some of those "lifetime pads" or "fleet pads". Those things wear rotors out before the pads wear out, and pad noise isn't uncommon with them. If thats what is in there, remove them, throw them away, put in regular pads, and never purchase those things again. Lifetime or fleet pads are junk. those would be my first two guesses at this.

Sometimes brake noises can be a HUGE pain. We had a newer Excursion that got new brakes. Started to have a squeal when the brakes were hot. This was, brand new Ford Motorcraft rotors, Brand new Ford Motorcraft pads. So after trying a couple things, we cut the rotors(brand new rotors). They weren't smooth at all(yay for Motorcraft?). But the noise was still there. Took out the pads and put in Ford OEM pads, sure enough the noise was gone. So even high quality pads can be junk sometimes.

Ooh, couple weeks ago I had a Mitsubishi Outlander that had a brake grind noise. The guy had run off the road and royally screwed the thing up. All four sets of pads had dirt embedded in them. Didn't want to change the brakes.... some people.

 

[newyorkin]

notice caliper to rotor clearances? I put new rotors and calipers on my 97 C2500, couldn't locate a grinding noise(sounded just like metal to metal pads, but pads were brand new). Finally I realized the caliper was rubbing the outside edge of the rotors(yay for aftermarket parts from Advanced Auto). Could more miles and the sound went away(makes me think it might not be your issue).

What kind of pads were installed? The fact that they've worn good ridges into the rotors after what you said 10,000 miles? makes me think they are some of those "lifetime pads" or "fleet pads". Those things wear rotors out before the pads wear out, and pad noise isn't uncommon with them. If thats what is in there, remove them, throw them away, put in regular pads, and never purchase those things again. Lifetime or fleet pads are junk. those would be my first two guesses at this.

Sometimes brake noises can be a HUGE pain. We had a newer Excursion that got new brakes. Started to have a squeal when the brakes were hot. This was, brand new Ford Motorcraft rotors, Brand new Ford Motorcraft pads. So after trying a couple things, we cut the rotors(brand new rotors). They weren't smooth at all(yay for Motorcraft?). But the noise was still there. Took out the pads and put in Ford OEM pads, sure enough the noise was gone. So even high quality pads can be junk sometimes.

Ooh, couple weeks ago I had a Mitsubishi Outlander that had a brake grind noise. The guy had run off the road and royally screwed the thing up. All four sets of pads had dirt embedded in them. Didn't want to change the brakes.... some people.

I think you're right. I don't remember exactly what I got, but I think they were "lifetime" pads. I remember trying to get the best quality I could get.

I guess I'll have the old rotors cut this week and get a new set of pads and see how that goes...

I thought about rotor to caliper grinding, but that looked clear and nothing shiny or rubbed looking.

Thanks for the quick replies, fellas!