Help, Single brake caliper sticking
Thread Starter
Racer
Joined: Apr 2001
Posts: 452
Likes: 0
From: Tulsa Ok, Racing the wind
Help, Single brake caliper sticking
I am helping a buddy figure out why his 90 coupe front passenger side brake caliper keeps sticking, eating up the brake pad. It's the only caliper sticking of the four.
Question: Can brake fluid pressure build up in one line and force the caliper to stay applied while the others release? Or other reasons?
Question: Can brake fluid pressure build up in one line and force the caliper to stay applied while the others release? Or other reasons?
Safety Car
Joined: Jul 2004
Posts: 3,845
Likes: 30
I am helping a buddy figure out why his 90 coupe front passenger side brake caliper keeps sticking, eating up the brake pad. It's the only caliper sticking of the four.
Question: Can brake fluid pressure build up in one line and force the caliper to stay applied while the others release? Or other reasons?
Question: Can brake fluid pressure build up in one line and force the caliper to stay applied while the others release? Or other reasons?
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Check the condition of the guide pins and if they have grease in them.
Very easy to do. Remvoe the two small bolts at either end of the caliper and pull it off the rotor (the pad will drop out so make sure you remember which is the inside pad and the outside pad!).
The guide pins pull out easily; just slide the small rubber boot off the retaining lip and pull the pin out. It should have grease on the pin and in the hole in the caliper body. If they are dry, I would suggest getting new guide pins. They will come with new bolts (with threadlocker already on them) and a small packet of grease for the guide pins. Torque these bolts to 25 ft-lbs.
If that isn't the fix, then do a complete flush of the brake fluid. It's possible that there is some material in the fluid that is blocking the line so when you release the pedal, there is still some pressure in the one line going to that caliper.
Other possibilities are a sticky piston inside the caliper or the flexible brake line going to that caliper is collapsing or has broken internally.
You didn't say what the mileage is on the car, or when the last brake job was done, but I would be replacing all of the flex lines, do a complete flush of the fluid using a good quality DOT3 fluid and replace all of the guide pins.
Very easy to do. Remvoe the two small bolts at either end of the caliper and pull it off the rotor (the pad will drop out so make sure you remember which is the inside pad and the outside pad!).
The guide pins pull out easily; just slide the small rubber boot off the retaining lip and pull the pin out. It should have grease on the pin and in the hole in the caliper body. If they are dry, I would suggest getting new guide pins. They will come with new bolts (with threadlocker already on them) and a small packet of grease for the guide pins. Torque these bolts to 25 ft-lbs.
If that isn't the fix, then do a complete flush of the brake fluid. It's possible that there is some material in the fluid that is blocking the line so when you release the pedal, there is still some pressure in the one line going to that caliper.
Other possibilities are a sticky piston inside the caliper or the flexible brake line going to that caliper is collapsing or has broken internally.
You didn't say what the mileage is on the car, or when the last brake job was done, but I would be replacing all of the flex lines, do a complete flush of the fluid using a good quality DOT3 fluid and replace all of the guide pins.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
After that, a good visual on the hard line to see if was crushed. And then everything else.
Thread Starter
Racer
Joined: Apr 2001
Posts: 452
Likes: 0
From: Tulsa Ok, Racing the wind
Great info guy's, we have replaced the caliper and that did not seem to fix the problem. We also replaced the flex line. I have the car up on my lift today and will be finding the slide pins, cleaning and greasing.
I am very interested in the ABS module, I really suspect that is the problem, Where can I find the module, is it in the engine compartment? What does it look like?
I am very interested in the ABS module, I really suspect that is the problem, Where can I find the module, is it in the engine compartment? What does it look like?
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
The ABS unit is in a compartment behind the driver. You will see all the lines to the unit. I have not worked on a 90 for ABS so I hesitate to give you any more details that might be inaccurate. I am more familiar with the 92-94s. I believe the brake computer in there also.
There are used ones one around from used part dealers. Also Ebay.
Good luck
There are used ones one around from used part dealers. Also Ebay.
Good luck
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Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The ABS pump is in the compartment behind the drivers seat. There is a separate procedure for bleeding the ABS so if you do install an replacement, it's best to have that procedure available or get it done.
Definitely do a complete fluid flush with a new ABS pump. If there's any chance of particles in the fluid somewhere, it's possible that it could wind up in the new ABS unit.
Use a turkey baster and suck out the old fluid from the master cylinder reservoir and fill with fresh fluid before bleeding.
Definitely do a complete fluid flush with a new ABS pump. If there's any chance of particles in the fluid somewhere, it's possible that it could wind up in the new ABS unit.
Use a turkey baster and suck out the old fluid from the master cylinder reservoir and fill with fresh fluid before bleeding.
