96 OBW, 209k

 

My breaks make a clicking or knocking noise. Sounds like it's coming from the front driver's side. I can make the noise stop by pressing the breaks even lightly. It sounds like the pads are knocking around. Also, the wheel shakes when I break at speeds over about 40mph.

 

This started over night, in a sense. I took my car off the road for about a month to work on the trans. Before it went down for the trans repair, the breaks were perfect, I had just done a break job changing the front pads and rotors, regreased everything, and changed the break fluid.

 

During the test drive after putting the trans back in, the breaks were making a lot of noise when stopping and the shake was present. I put it down to all the surface rust that had developed while I had it off the road and figured it would work itself out. The grinding noise went away, but the shake never did and I soon noticed the clicking.

 

My guess was that the driver's rotor had a rust booger on it that didn't want to come off, but when I dug into it, both rotors looked fine.

 

Theories? Suggestions?

 

Thanks!

 

Will

check the little metal spring clips that hold the pads in place, one or more may be missing

You might also check the piston or pistons(my 99 has 2). I had a similar noise, checked the same stuff as you, found that one piston was hanging up due to a torn rubber boot and subsquent rust. Bob

We deal with this quite often at work (car dealership) most often on our used cars. Usually it goes away after being driven really hard a few times. If not you'll have to have the rotors turned.

The bolts the caliper slides on may have dried out it's grease. Pull the bolt, swing the caliper up and then slide it off the other pin/bolt, pull the bushes out of the caliper, the ones the bolt goes through... in behind a rubber boot, lube both of them, the bolt and the pin, put it all back together again.

check the little metal spring clips that hold the pads in place, one or more may be missing

 

All present and accounted for.

 

We deal with this quite often at work (car dealership) most often on our used cars. Usually it goes away after being driven really hard a few times. If not you'll have to have the rotors turned.

 

As I said in the post, the rotors were replaced less then three months ago, and one of those months they were not being driven. Even though surface rust had built up from sitting, that all went away as the car was driven. I pulled them both off and they both look fine. I didn't check them for runout, but I don't see how rotors could warp from sitting for a month:-\

 

 

The bolts the caliper slides on may have dried out it's grease. Pull the bolt, swing the caliper up and then slide it off the other pin/bolt, pull the bushes out of the caliper, the ones the bolt goes through... in behind a rubber boot, lube both of them, the bolt and the pin, put it all back together again.

 

Nope, these were regreased when I did the brake job. That grease was still present and the calipers slide easily along the post.

 

You might also check the piston or pistons(my 99 has 2). I had a similar noise, checked the same stuff as you, found that one piston was hanging up due to a torn rubber boot and subsquent rust. Bob

 

All of the piston boots were intact and my pad wear was even on both sides when I did the brake job so I left well enough alone, but this will be my next step. Maybe I missed something, or more likely the humidity allowed moisture to settle in there which never got cooked off with daily driven brakes.

 

Thanks for everyone's input.

 

Will-

As I said in the post, the rotors were replaced less then three months ago, and one of those months they were not being driven. Even though surface rust had built up from sitting, that all went away as the car was driven. I pulled them both off and they both look fine. I didn't check them for runout, but I don't see how rotors could warp from sitting for a month

 

Its not that they're warped, they just not "flat" anymore. Where the rotor is exposed, more of the surface is "eaten away" by rust. Under the pads the effect is not as bad because less oxygen can get to that area to oxidize the surface. So you end up with a high spot on the surface of the rotor. It's not a huge difference, but it's enough to notice when you hit the pedal.

I see what you're saying, I'll take a light turn on each and see how that does.

 

thanks

 

Will-

If you have a caliper you can measure the width of the rotor in a dozen or so places around the circumference of the disc and see if there is a certain place where its thicker. You could also check the run out if you have the right rig to do that with. Either way would tell you if the surface of the rotor is out of spec.

Yeah, I've got a caliper, what is the allowable variation? I can turn the rotors at work (I'm a machinist) but it means a 100 mile drive round trip, so I don't want to take the drive if I don't have to.

 

thanks again

 

Will-

Usually the maximum run out that you want is gonna be about 0.005". Anything above that and you'll start to feel it. I'd say if you find any spot that is more than about .008" - .010" wider than the thinnest spot on the rotor than you probably will want to turn them.

right on, thanks for the figures

I agree with fairtax, it could very well be a rotor. I bought two new ones for the front of my Legacy wagon and one was bad right out of the box.

 

However I no longer turn my rotors, It dont cost much more to buy new ones. And after they are cut down they warp very easy.

Edited August 21, 200916 yr by tcspeer

They are cheap, between the drive and the time it will take me to turn them and drive back, it's tempting to just buy two new ones. Maybe I'll check for a warranty, after all they are only a few months old.