[curtjames37]

So, my brakes have been sticking lately. It can be either the front passenger or the front driver side. It is usually the passenger side and is hardly noticable. It will make a high pitched "chirp" maybe once every second and varies with speed. It also goes away once braking. Today, though, it was both sides and it was very noticable. I burned my finger pretty good when I touched the caliper.

Here's what I've done so far:
Replaced both calipers - no change.
Replaced both rotors/pads - no change although I wasn't expecting one.
Checked the brake lines - no noticable damage fluid flows good when bleeding.

So, what do you guys think? Master cylinder? Brake booster? I am at a loss here and don't want to just throw parts at it. If it was the master cylinder wouldn't it be both sides all the time? What about the booster, wouldn't it be all the brakes?

Help me out here!

[bee guz]

Did you take the slides apart and use a high temp. grease on them, they might just be lazy moving back, clean them up good, and make sure the move easy.

You can have someone stomp on the brakes, with the wheels off the ground, and quickly spin each wheel to see which one, if not both are sticking, they should relaese quickly, after you assistant releases the brake pedal.

[curtjames37]

I did lube the slides well and they move freely. I will get a buddy to help me with what you suggested.

[bee guz]

Ya if you have someone there, to help you, I tried doing it by myself,impossible to get there fast enough, to feel it stick, unless its really bad.

I had a chev. that had a rubber line with an obstruction, it acted alot like that, as you would brake, the fluid would go to the caliper and be slow to return, causeing the brake to stick, it should hold and immidiatly release, when you lrt go of the pedal,,, Hope you find it, look for crushed steel lines too, that will act the same way... I just tought of something, hows the fluid look, if its black, and small peices of debries in it that may be it

[curtjames37]

My buddy is going to come over tomorrow so we will give your suggestion a try then. I messed with it some more today though.

Here is what I learned:
1) It is both front brakes.
2) It is much more so the passenger side than the driver side.
3) If I push the piston back into the caliper and drive it around it won't start to stick until I have driven for 30 minutes or so.
4) I ****ing hate bleeding brakes
5) Once it starts sticking, it will not let go until you take the wheel off and manually push the piston back in.

The fluid is clear because I just flushed it about a month ago.

[filluptrk]

From the manual you have eliminated seized calipers, and caliper binding. That leaves loose/worn wheel bearings, loose caliper mounts, mis-assembled components, long booster output rod, a blocked master cylinder return port, or a faulty power booster that binds up not fully releasing.
In the booster is an atmospheric inlet valve activated by the brake pedal. When it opens it allows the vacuum to assist braking. I am thinking that it might be possible if the booster had a leak in that valve to allow the vacuum assist to apply the master cylinder slightly causing the drag. As the brakes began to slowly heat up it would get worse. When you apply the brakes then let off, the pads retract, only to be again pushed back by the booster leak starting it all over again.
Being a shade tree mechanic I'd pull off and plug the vacuum line from the booster and drive it around, not in rush hour traffic, and see if you get the same dragging brakes. If not, I'd guess it is the booster.
There is also a Pressure Differential Valve, and a Proportioning Valve in the system, but neither is listed as a source of brake drag. Phil

[curtjames37]

Originally Posted by filluptrk

From the manual you have eliminated seized calipers, and caliper binding. That leaves loose/worn wheel bearings, loose caliper mounts, mis-assembled components, long booster output rod, a blocked master cylinder return port, or a faulty power booster that binds up not fully releasing.
In the booster is an atmospheric inlet valve activated by the brake pedal. When it opens it allows the vacuum to assist braking. I am thinking that it might be possible if the booster had a leak in that valve to allow the vacuum assist to apply the master cylinder slightly causing the drag. As the brakes began to slowly heat up it would get worse. When you apply the brakes then let off, the pads retract, only to be again pushed back by the booster leak starting it all over again.
Being a shade tree mechanic I'd pull off and plug the vacuum line from the booster and drive it around, not in rush hour traffic, and see if you get the same dragging brakes. If not, I'd guess it is the booster.
There is also a Pressure Differential Valve, and a Proportioning Valve in the system, but neither is listed as a source of brake drag. Phil

Okay, I took a look at the wheel bearings and caliper mounts today and everything is as it should be. Everything it assembled correctly so we can rule that out as well.

I am liking the booster idea but if it was the booster would the brakes still drag even after the engine is turned off? It doesn't matter how long you let it sit until I push the piston back into the caliper it will not let go. I did drive around the neighborhood today for about 20 minutes without the booster connected and there was no dragging at all.

I guess I will replace the booster and see how it goes. If anyone else has any suggestions I would appreciate it.

[bee guz]

Ya I had a mazda, that did that, the boster kept the pressure on the master, I had to drive it till the weekend, I couldn't get time off to repair it during the week, so I opened the bleeders and slightly stepped on the brake, and drew some air in, and closed the bleeders, other than having to pump the brake to get it to stop, I made it to the weekend, to repair it.

Good glad you found it....

[curtjames37]

I got the booster replaced earlier today and it solved the problem. The pedal also feels much better now, too. Thanks to everyone for your help!

[curtjames37]

Well I guess I spoke too soon. After driving today both front brakes started dragging again. Out of complete frustration I replaced the master cylinder and the rubber brake hoses today. No change.

Here is what it is not:
Calipers (Including the slides)
Hoses/Lines
Master Cylinder
Power Booster

Aside from the proportioning valve, that completely eliminates all of the hydraulics. So, what is left? The wheel bearings seemed fine. Could the proportioning valve be the cause? I would appreciate some help.

[filluptrk]

Does the brake pedal fully retract? Could anything be causing it to bind keeping the master cylinder from working properly? There has to be clearance between the rod coming out of the booster and the piston in the master cylinder. Maybe try putting a rubber band on the pedal to ensure total return and see if it makes any difference.
You may have to take it down to a shop that specializes in brake work only, sometimes experts are worth every penny. Good luck, Phil

[Goldenknob]

I would have guessed Master Cylinder but you've fixed that... unless your new master cylinder faulty. so do you have ABS brakes?

[curtjames37]

I am 90% sure the pedal is fully retracting but I will try the rubber band thing. I do not have ABS brakes. If I can't get it figured out today I guess I will have to take it somewhere.

Appreciate the suggestions guys... keep them coming.

[curtjames37]

Well, I'm throwing in the towel. I'm taking it to a brake shop in the morning. I will let you guys know what it turns out to be.

[curtjames37]

I got the Jeep back from the mechanic last night and he says he is 90% sure that it is the proportioning valve. I ordered one from the dealer and it should come in sometime today so we'll see how it goes.