scoutski

I have searched the forum but can't find any help with this problem; I have an 02 Sub 1500,bought new, it had a squeaking noise in the rear, pulled the wheels and hubs and found the parking brake shoe on the drivers side down to the metal. This is strange because I never use the parking brake! Went ahead and replaced the parking brakes as well as front and rear pads. This was the original pads, 104000 miles. Now the rear brakes are failing to release pressure after the brakes are applied. If I wait for 10 to 15 minutes the calipers slowly release their pressure! When I drive it the rear rotors get hot and it stinks. It feels like the brakes are still on when I start from a stop. Need help!

73shark

A possible cause of the rear caliper sticking is a collapsed inner brake hose liner. When that happens, it acts as a check valve.

in2pro

Have the calipers even been bled? if not that would be an inexpensive place to start, bleed and flush the brake lines with new fluid...

The next Item I would think would be the caliper itself if its just one doing it, but its plausible that both have gone bad...

the next possibility is the proportioning valve...

And lastly the master cylinder is bad

my 2 cents of internet troubleshooting

scoutski

Appreciate the comeback, I replaced the brake fluid last year and at that time I bled all four calipers. Been driving it all year without any problems.
Both sides are locking up, so I ruled out a collapsed hose.
I have been going thru everything that I did and the one thing that stands out in my mind is; After I put it back on the ground and started to back it out of the carport, I hit the brakes and they went to the floor. I had all four calipers calipers retracted so I immediately knew that a quick pump and the brakes would be fine. What I am thinking now is that I should have pumped the brakes with the engine not running. Maybe this caused the ABS to throw a code and now I have caused a problem. I don't have a scanner nor access to one other than the stealer.
Any thoughts?

in2pro

Do you have a check engine or service engine/ABS or a brake warning light on?
Most code readers will not check ABS codes, the scanner has to have that specific function...

scoutski

Yes, it did have the check engine light and the ABS illuminated when I moved it to retest it. Within one minute both lights went out and did not come back on. I drove it up the road about one mile and back. I then lifted the rearend with it in neutral to check the rear wheels. Both refused to turn but again, after several minutes they began to free up.
Where is the "proportioning valve" located? How does one go about checking to see if it is functioning properly.
Thanks in advance.

scoutski

Back at it again! Had to stop working on it to go fishing. The Fall Flounder run started so that takes priority over wrenching.
Pulled the left side caliper to check the pistons. I could not get them to budge with compressed air at 135 psi. so I reattached it to the brake hose and with a clamp in place to keep them from blowing out. I had the wife push the brake peddle as I unscrewed the clamp, they began to move out. When they were close to passing the inner seal I stopped. Then I removed the brake line and took the caliper to the bench where I pulled the pistons out with my hand.
I have never had pistons that were this difficult to remove!
Removed the outer dust sheilds and the inner O-rings, cleaned the housing and pistons. Wanted to test fit the pistons without the O-ring. both pistons seemed to be swolen and would not fit back into the caliper? Now I am wondering if the phenolic resin swells with time? Have any rebuilders out there seen this? Oh yes, I did get my limit of Flounder all three days, plus a few Reds and Trout. Lake Calcasieu La.

scoutski

Decided to find out if the rear caliper pistons could be freed up. Here is what I found and did to fix it. I cleaned the phenolic pistons with 280 grit sandpaper then followed up with 400 grit. Did this in the sink with the water running on the part being sanded. The pistons appeared to have a buildup of a varnish like substance on them. I test fitted them several times while sanding. I only cleaned the upper third of each piston.
I had to order the rebuild kits because no stores in this town sell them. In the meantime I had to reuse the old parts that I carefully removed.
Reinstalled the calipers and bled them. Now the rear pads no longer bind after applying the brakes. As soon as my parts come in I get to do this all over again!!!

in2pro

Now that is real DIY repair
I wonder if maybe a strong solvent would have also removed the varnish...
brake cleaner, paint thinner etc.....

Take a few pictures of your rebuild and post, it would make a great helpful how to

scoutski

I did try brake cleaner at first but it didn't touch the buildup on the piston. I didn't have any acetone or MEK on hand to try or I would have. I also tried scotchbrite with little success, the last resort was to wet sand them.
The easy thing to do was to throw a bunch of new or rebuilt parts at it but that would not have identified the root cause. When the new caliper kits arrive the rears will be as good as new. I have had problems in the past with the cheap rebuilt parts that are on the market these days.

Scoutski