Front brakes screeching when standing still. SOLVED!

In the past few weeks I have noticed that my front brakes emit a screech like dry metal on metal type sound (or like the old floor board when you walk on them) when standing still (car can be "ready" or off, it doesn't matter, it can be in park or in D, also doesn't matter) and applying the brakes hard. Such as at a red light. If I apply the brakes harder than just to keep the car from moving the screech happens and I can modulate it with the brake pedal pressure. I can sort of "play a tune" with it if I really try, by pressing the brake pedal just right. Drove me nuts, but the brakes worked perfectly fine. Car stopped very well and no codes related to brakes at all.

Since I haven't done the caliper pins on this car yet, I decided to do that. I took the calipers off the bracket, took the pins out, cleaned and relubricated them and put everything back together and screech did not go away. I drove around with it for a while and finally decided to do some investigating. I asked my wife to sit in the car and "play" the screech sound with the pedal while I listened and investigated around the front wheel. As she made the sound I was able to pin-point it to the caliper. So I took the caliper off again and figured that it may be just where the piston is at the moment that is squeaky. So I pushed the caliper piston all the way back into the bore with a large set of channel locks. Then re-assembled everything and pressed the brake pedal a few times to return the piston to where it needs to be. Sure enough the sound was gone from that side. I did the other side and now no more screech!

I think this is a fairly common problem and I have not seen a solution yet. People report that it goes away after they replace the pads and that makes sense since you need to push the piston back for the new pads. My pads are only about 1/3 worn, so I am not replacing them any time soon and it's nice to be able to fix this without unnecessary part replacement.

Hope that helps some one in the future.

 

It does it when moving too, but it's less pronounced, so I specifically state that it does it while not moving. As the car is parked and off, you get in and press the brake pedal to the floor at some point in the pedal movement a screech appears as the rotor is being squeezed harder by the caliper. As you lighten up on the pressure the screech changes and goes away as the pressure eases. No movement of the car is necessary. The noise comes from the (very slight) motion of the caliper piston through its bore. There is a spot on the piston that makes a noise. By pressing the piston in and having it work its way out again, perhaps the spot got cleaned up. It may come back again for all I know, but for now it's quiet.

 

Yes, the wear indicator is not what's making the noise. For the wear indicator to make a noise the rotor needs to be turning. This noise happens when the car is stationary as well as moving. And it only happens under a certain greater than usual pedal pressure. I can drive all day and not make a noise if I am careful. But if I step on the brake with a bit more force, it'll screech. I should have made a recording of this.

 

A few days on now and I hear the noise coming back again, although in smaller quantity. I can see how changing the pads will solve this. It will move the piston to a different position than where it makes the screech. I am not sure what exactly the root cause is, I would need to take apart the caliper to see that, but I imagine it's something like a wear line or something that is on the piston and when it gets to that point in piston position it creates the noise. Again, it only happens when the brake fluid is pressurized in the caliper and it comes from the caliper. If it gets as bad as it was I will repeat the procedure and see if that keeps it at bay longer.

 

Update: A little over two weeks since I performed the piston push back and got rid of the screech, it's back. I noticed it coming back little by little over the last few days and now it seems to be as bad as it was before. I will try to record the sound and post the audio here for reference. Again, brakes work perfectly, no codes. Just the annoying screech that probably only I can hear and care. Most people in the car are blissfully unaware of it, but I am very sensitive to car noises since I've been wrenching on my own cars since I was 16 (back in the early 80's).

So now my theory is that there is some sort of wear line at that particular place on the piston and when it gets to that it starts to screech and the line is moving in and out of the bore. I am less 50% on the wear of the pads and I am sure that newer thicker pads will cause the noise to go away until the new pads wear down to about the same thickness as they are now. I may just throw a new set of pads in there, it's easy and probably inexpensive protection of my sanity.

 

It's on both sides and the noise does not bother me worth two calipers Also, I could just put a new set of pads and make the noise go away for a good long while with more pad material.

 

Yes, exactly. Probably there is a line of corrosion or something at that place in poison travel. It does not happen much. Only when applying brakes fully at rest or when stomping on the pedal and hydraulics put a lot of pressure on the caliper.