Subaru Brake Squeal

Does it change much with sweeping turns left or right? Also, is the temperature of one hub hotter than it's companion? You should also try to SAFELY have someone pace the car, on foot or bicycle, in a parking lot to see if they can hear anything from outside the car.

Carl

Yes, it does change with sweeping turns. Im not sure it the hub temp issue, but i noticed an uneven wear pattern on the left disk brake with NEW rotor and pads and OLD caliper.

the NEW caliper fixed the rotor wear pattern, but the squealing persists.

as for the sound, it can definately be heard with the windows down inside the car. It's so annoying, loud, and high pitched (imagine a lot crickets chirping simultaneously)

thanks for the input Carl.

Could be the caliber piston isn't getting pushed all the way back. That is, you release the brake pedal but the piston doesn't move all the way back so the pads are still slightly riding on the rotor. Could be rust on the piston, the seal on it that's gotten stiff with age, or rust on the sliding pin so the caliber doesn't slide on that side so the pads are at a slight angle and might be riding the rotor (I've got that now and will have to see if I can clean it or have to replace with a rebuilt caliber). My mom's Subie had the squeal when the pedal was released which the shop didn't find the first time until I got the guy to ride in the car so I show exactly under what condition the squeal occurred in a big empty parking lot. They then found a pebble stuck in the pad.

Also delamination of the brake hose can cause the piston not to return.

Blair

Although the sound is odd for a bearing, one characteristic of wheel bearing failure is the change in sound in turns. If the sound is worse on right turns, the left side bearing will be more heavily loaded from body roll and will sound worse/louder. Obviously left turns more severely load the right side. Sticking caliper on the pins OR sticking piston might show very unequal wear between inner and outer pad (inner heavily worn) as well as higher wheel temp after extended driving. I have also experienced a loud squeal in the past from a pebble stuck behind the backing plate on a Datsun.

Carl

Vanguard- Thanks for the advice, but I stated above that I replaced the old caliper with a remanufactured caliper and the squealing persists. Likewise, there is anti-rattle compound (really sticky stuff) on the back of the pad so that the pad is literally "attached" to the new caliper piston.

Blair- Delaminated brake hose? Can you explain?

Carl- When I assesed this problem for the first time, I went in there to replace a Constant Velocity Joint. I did not notice any debris on the dust pan, but afterwards, the dustpan was contacting the rotor just a little bit and was blatantly obvious, so I bent the dustpan back so there was no more contact. and yet the squealing is still there. Thanks again Carl.

Obviously, the high pitched squeal is caused by the brake pad touching ever so slightly on the rotor, meaning that something is not releasing properly. This does not make sense, however, because the whole assembly is floating (rotors, brakes). Yet, I cant fathom why a bad wheel bearing would make a extremely high pitched noise.

Over in the Ford truck group it was discussed that sometimes the brake lines to a single wheel would delaminate inside and would act as a check valve allowing brake fluid to flow out to the caliper and when pressure was released the fluid would maintain pressure not allowing the caliper to release causing the brake to squeak.

You can search alt.trucks.ford

Not a common occurrence, but it looks like you have exhausted all of the more common ones.

Blair

You are correct and, I've been told, hydraulic in general can have 'flappers' inside that cause a check valve-type behvavior. Worth considering but I'd still expect the offending brake system to wear unevenly and produce heat.

I dunno

Carl

Blair - That is very interesting. I never would have though of that. I'll look into that some more. Thanks for the insight.

Carl- The uneven wear pattern was fixed by installing a new, remanufactured caliper. Thanks, I'll definately look into the hydraulics.

Now Ive heard another "myth": Could it possibly be caused by a failing Anti-Lock Braking System?

Im confused by the fact that i have a new caliper, new rotors, and new pads and the system is still squeaking. It's really throwing me off that the squeaking goes away when i apply the brakes. I just dont know.

Defiantly should produce heat. If it is bad enough, you should be able to raise car off of the ground and have someone press the brake and release, and should be able to feel a difference between the drag on one that is working and the one that possibly does not release.

Blair

Well, finally someone with the same problem as mine. I have been fighting this for a year with my daughters 97 Legacy sedan. The symptoms are identical with the exception of one thing. It doesn't always do it. I've had the wheel, caliper and pads off and put anti-squeel goo on the pads. I thought I got the wrong wheel so I took all four wheels apart and did the same thing. I checked all the backing plates for clearance to no avail. There is no abnormal wear on the rotors or pads. It seldom does it when I am driving, but it drives my daughter nuts as she drives it everyday. If we come up with any answers here, I would be most interested.

Regards and Good Luck

Blair -Thanks, I'll have to try that method. When i first start the car, i can hear the brake pad contacting, without my foot on the brake (its like the sound one gets while driving with a very light rust on the rotor). Not sure if that helps, though.

Jim- I know exactly what your daughter is going through. The sound is so annoying and makes everyone turn heads to see where it is coming from. However, I am experiencing your same problem. The breaks squeal completely at random. I drove 10 miles to the store and had absolutely no squeal on the way there, but on the way back, it really started to squeal.

Things I've noticed:

- The squeal occurs very randomly, usually inbetween the brake pad's respective "cold" and "hot" range; although the squeal came driving at

65 mph highway speed. Other times, the brakes start squealing at the first stopsign in my neighborhood.

- The squeal is a very metal-on-metal high pitched squeal, indicating that "whatever" is touching is contacting very slightly

- The squeal goes away when I apply brakes.

- The squeal changes tone and/or disappears while turning, even a very slight turn.

- Somtimes I can make the squeaking noise by slowly releasing the brake while coming off of a red light / stop sign. The squeak generally increases with speed, turning into a constant whaling at high speeds, say 40 mph.

Out of all the brake problems I've seen, this one takes the cake.

Sorry for the double post, but i forgot to include one last thing:

This problem started when Advance Auto gave me the wrong size pads for my Subaru. They were just 1-2 mm too big so I took 1 anti-rattle spring out to accomodate. Things generally went downhill from there. The brake pedal went to the floor, and there was a signifigant reduction in braking power. So, I replaced the master cylinder, but that didnt help.I replaced the oversized pads with the correct size pads, and a few days later, the squeaking began. Suspecting that the rotor had gotten bent due to the oversized brake pads getting stuck in place (which i suspected was the reason that the brake pedal was going to the floor), i replaced the old rotor with a new rotor. Then i noticed an uneven wear pattern on the squeaking rotor (Left Side Disk Brake) so I figured that the caliper had gotten bent (somehow). Then I replaced the caliper, and the abnormal wear pattern was fixed but the squealing persisted. Now here I am.

The ONLY things I have not replaced in the entire braking system are the brake hoses and the Caliper Support Bracket. I just dont see how the forces involved in braking with oversized pads could possibly have bent the caliper support bracket. Obviously something wierd/ambiguous is wrong with my left disk brake, and im just hoping it doesnt have anything to do with the steering knuckle or wheel bearing.

Thanks a lot for the advice.

One thing I did emediately before the squealing started was replace the back brake pads and had the rotors turned. The pads had been overheated and were alittle burn't looking (both sides) The rotors had some slight surface looking irregularities from the heat, but they turned out with just 10 thousanths off. I would normally not turn rotors, but this car only has 30K on it. The previous owner lived on a hill and rode the brakes all the way to the bottom. I think it is the right rear that is causing it, seems wierd since turns seems to make it worse. Braking does make it stop, but it has to be a reasonably good stop. Gradualy applying the brake make not stop it.

Regards, Jim

I had this problem on my 99 OBW. One "cure" that works for a while is to remove the pads on the offending wheel (mine was rear left) and grind a 45 deg angle on the edges with a file. I ended up with about

1/8" lip all around the pad. Then I roughed up the disk rotor with a disk sander with a 120 grit pad to lightly scratch the surface. I also roughed up the pads slightly. I'm not sure which step solved the problem, but it worked for quite a while. Now the noise is starting to come back, so I suspect I need to repeat the procedure. I think what's happening is my wife drives the car lightly and doesn't hit the brakes hard at any point so they end up glazing the pads and rotor. One thing to try before doing the above is to bring the car to a few "hard" stops, one right after the other so the pads/rotors get hot and the glaze gets removed.

As for the treatment of the brakes after re-assembling (or, indeed, after replacing pads) check the tech paper at stoptech. good info there I believe;

Carl

Careful: if you've got it up on a lift, it's possible that you may not notice any contact with the dust shield. Look for kinks, bends, or other imperfections. If it appeared to be in contact once, it's possible it still is.

The various weight affecting it in that other fellow's car is precisely the symptom I had with my old '02 WRX. It was a dust shield in all cases that was generating the noise.

rd- Thanks for the insight, but im not sure i want to permanently grind new pads and rotors.

Carl- thanks for the the website. I tried a series of high-speed stops (a series being 2; the website reccomends 10 high speed stops) and it fixed the problem for a few minutes, but came back again.

k. ote- I cant believe i did not think of that. I inspected it on a scissor jack. Im going to go out and look to see if there is any contact with the dust plate.

Thanks a lot for the help.