Mechanics

CHEVY FRONT BRAKE CAILPER WON'T RELEASE

1995 Chevrolet Lumina

Brakes problem
1995 Chevy Lumina 6 cyl Front Wheel Drive Automatic 91,000 miles

Yesterday I noticed a brake pad burning smell coming from the left front wheel well. When I got home I noticed that smoke was coming from the wheel opening along with the brake pad smell. I removed the wheel and noticed that the pads were tight(locked) against the rotor. The rotor was very hot. I removed, after it cooled down, ( with great difficultly) the caliper and assumed that the caliper piston seized up. I replace the caliper, again assuming that it was the caliper. Well, I assumed wrong. The brake pads still grab the rotor. There are no lights (ABS, check engine, etc.) On the dash. I disconnected the two electric connections that go to the ABS unit in the engine compartment to see if this would make a difference and it did not( except for the ABS light did come on then). Please let me know what I should be looking for next to troubleshoot this problem. I do own a code reader for this vehicle; however, being that no lights came on the dash, I have not used it yet. The vehicle is the Lumina APV with the 3.1 V6. Thank you, Steve
Avatar
Sirjr
July 17, 2009.




Sounds like a collapsed hose or fluid restriction beyond that. Drive it shortly, then pop the bleeder and see if fluid comes out. Make sure the hose is not twisted.

I bled the line to the caliper, fluid did come out. I will update you on how it works. Thanks for the quick response as I'll be able to use the car.

Tiny
Sirjr
Jul 17, 2009.
I think the problem will still be there. Check for fluid flow when the problem is happening.

First if there is flow when its hot and also if the wheel releases when the bleeder is opened.

Also, look at the pad abutment surface on the knuckle. This is where the pad slides back and forth. Grooves can get worn into it and not allow the pad to move.


http://www.2carpros.com/forum/automotive_pictures/30961_apv_1.jpg


I will look at the knuckle for grooves( thanks for the great diagram). I used the vehicle today (150 miles) and it seemed okay( no burning, no grabbing of the brake when I put it in neutral). When I got home today, I had to change the oil. When I had the car jacked up, I rotated the wheel and it was free; however, I did not take the wheel off. If I do find grooves in the knuckle, what should I do next?
AD

Tiny
Sirjr
Jul 19, 2009.
HUH....maybe the bleeding worked....

Well, the least expensive way to fix it is to clean the groove out good and fill the void with a epoxy filler. I've used liquid metal. Then after it is hard, file it flat and lubricate. Replacing the knuckle is the other option.


http://www.2carpros.com/forum/automotive_pictures/30961_caliper_lube_21.jpg


The lower knuckle is rough (bumpy), but no grooves. I lubricated along the knuckle that comes in contact with the lower part of the of the outer brake pad. Although the rotor rotates freely now when the brake is released ( when I had it jacked up), when I let the car roll on a hill after I stop, when I let off the brake, there is a sound, the best I can describe it, is a groan-like sound that emanates from that wheel/rotor. There is no burning smell, or drag at all now when I release the brakes. The car now rolls freely when I release the brake, in neutral, on a hill. Prior to replacing the caliper, the car remained in place, as if the brake was still applied. I will see if the " groaning" sound disappears now that I lubricated the knuckle.

Tiny
Sirjr
Jul 20, 2009.
Sounds like progress is being made. IS the noise from that wheel for sure? Can always isolate by pinching off brake hoses.

I like to remove and roughnesss when I do a brake job and get it right down to a clean,smooth surface.

On the lube side, I should have put this up.


http://www.2carpros.com/forum/automotive_pictures/30961_caliper_lubeareas_20.jpg



http://www.2carpros.com/forum/automotive_pictures/30961_caliper_lubeareasbrack_21.jpg



Obviously not the same caliper set up, but you get the idea.

I drove the vehicle this morning and it seemed fine. Thanks for another great picture on the lubrication points( I only wish that these pictures would be in my Chilton/Haynes manuals). I did lubricate all the caliper points. This morning when driving to my office, my wife informed me that the " groaning" sound I mentioned in the last post has always been present. We purchased the vehicle over five years ago with 56,000 miles. I replaced the front brakes pads at 85,000( I do not know if the pads were replaced prior to this) and have never had any issues with the braking system until last week. After you pointed out to lubricate the knuckle part that intersects with the outboard brake pad, I will do the passenger side as well and inspect the knuckle surface as well. Over the years I've encountered alot of strange(PC correct term) things that happened with my GM vehicles; however, last week's event was a first for me. Again, I appreciate your help and follow up posts. I will update you on how the van is functioning.

Tiny
Sirjr
Jul 21, 2009.
I use napa ultra premium rotors and napa adaptive one pads for elimation of brake noises caused from pad/rotor contact.

Been driving the van since my last post and everything is working great! Thanks so much for your help as you saved me from a lot of aggravation.

Tiny
Sirjr
Aug 2, 2009.

AD