99 S10 Blazer 4x4 Rear Brake Problems

[bwood]

Working on my Mom-n-Laws Blazer, did new disc and pads all around (4 wheeel disc). Her rear disc pads were chewed up and I replaced the rotors as they were pitted bad from the factory. I put it all back together and took it for a drive. The rear calipers are dragging pretty bad, probably why they were in such bad shape, the truck only has about 60k on it. Its not the parking brake, it is loose and working properly. Its got to be the center rear brake line or the master cylinder for both to be screwing up. I've drug on this far to ask if there are any known issues on these trucks with the master cylinder? Neither are a big deal to me, but its her money I have to spend, so I want to hit the nail on the head the first time. I'm going to try and blead as much as I can and get some fresh fluid in it as the master cylinder looks pretty nasty. Anyway looking for any pointers, its been awhile since I've done any work on the S Series trucks, I used to have a 99 and a 91.

[68C15]

were both the inner and outter pads evenly worn? it's possible that the caliper pistons or more likely the caliper slides are binding. these two scenarios would cause pitted rotors and uneven pad wear.
do the brakes function normal?
FYI GM used some real crappy metal for the rotors and substandard rear caliper mounting.

[old Rusty C10]

im betting a good flush and a new rubber line will help the situation .. although if the inside of the line went there could be crud in the calipers too

[bwood]

I don't remember on the pads, but I think they were even. I have the discs in the back of the truck. The pitting on the discs was more of a quality issue than wear. It looked like there was air in the metal when it was cast. When I was trying to remove the calipers, I couldn't get the calipers to release enough to slide them off. I had to crack the bleeder and then use a screwdriver to force it open. This was the same on both sides, so I think the problem is between the calipers and master cylinder. I finally got some time to work on it, and the battery was dead, so I couldn't get it to the driveway. I charged it last night and this morning then put it on the maintainer so maybe I can get to it tomorrow.

[old Rusty C10]

that seems to reek of the rubber line

[68C15]

^^^
I am inclined to think otherwise as these have a separate line for each wheel.

the "pitting" on the rotors is most likely due to the pads overheating and cooking the bonding adhesive out through the friction and depositing it on the surface.

I would have to do some digging but it may be possible you have a problem with the ABS unit.

[bwood]

The rear of the truck has (3) rubber lines, (1) for each caliper and (1) from the chassis to the axle. My thought is the one from the chassis to the axle. The front rotors were the same as far as the pits go. My Uncle's 98 Z28 was the same way. I'll take some pics of the rear rotors tomorrow and post them. I did some reading on the pitting and found many other posts on the net about pitting on the same vehicle. For the most part they were all late 97-00 model 4x4 S10 Blazers. Wathcing the baby tomorrow until late so its looking like Tuesday before I can get on it, maybe.......

I finally got to the squeaking under the wife's Malibu and found both the idler and tensioner pulleys singing. Pulled them and noticed a loose bolt in the alt/tensioner bracket, tried to tighten it and it is stripped. So now I'm looking for a right angle drill so I can get to the hole on the back of the engine for a HeliCoil. It calls for a 13/32" drill which is about 5" long and my smallest drill is about 7" and I've only got about 10" of clearance to get the bit perpendicular to the aluminum head where the hole is. So, Wife's driving my truck, and I'm borrowing stepdad's.

[bwood]

Well, the planets lined up today and I got the rear hose swapped and the system bled. No luck, rear calipers still not letting go. As far as I can tell, I only have two more options: master cylinder or ABS module. I'm leaning more toward MC. It has a lot of scum in the resevoir and I can't think of a reason why the ABS module would have the calipers locked down, especially if its not powered up.

[old Rusty C10]

if there is gunk in the system flush it out before you spend on a master

[bwood]

Thats what I did today. I used my vac pump and sucked the master out and put some cheap DOT 3 in and sucked it out again. Topped it off, then I put the new hose on. Bled a quart through each wheel and got clear fluid at each wheel, took awhile and now I owe the wife a night out, but I think I got the majority of it out. The gunk is mostly a film on the inside of the resevoir that I don't think I will be able to get out.

[bwood]

Well it looks like I got it. I may have been dealing with multiple issues. I picked up a master cylinder yesterday and put it on today. It seemed to actually make it worse. When I put the old MC in the vise to check it out, the port for the rears was weak, I could hold the pressure with my finger and keep it from shooting out. The new one, well, it was strong enough to shoot the threaded plastic plug out. Both ports on the new one seemed like it should. Installed it, bled it all again and then the rears were so tight, it was like I was holding the brake. I would barely move, and before it would move, just felt like the parking brake was on. So, I scratched my head for a while and began to question the stainless braided line that goes from the MC to the ABS controller, but changed my mind and went to the rear calipers. Cracked the bleeder and used a C-clamp and loosened it up and removed it. Took it to the bench dumped the old fluid out, put the air hose on it with 145 psi and the piston wouldn't budge. Kept on but still nothing. Ended up taking a drift punch and reaching in the fluid inlet and forcing the piston out and trying the air again. Finally got it out and low and behold, the phenolic piston was deteriorated and the bore was full of debris. Pulled the other side, with the same results. Trip to Oreilly for two calipers and some more bleeding, and all is good. This one really kicked my rear. I hate messing with brakes, I always end up pissed and broke with brake fluid stains all over the drive way. While this Blazer has been sitting in my driveway, the water pump started leaking, battery died, alt started growling and both the idler & tensioner pulleys had to be replaced. Not to mention I replaced the rear center brake hose. I never concidered the calipers as I didn't believe both would fail at the same time. Tomorrow I'm taking the alt and batt to Oreilly's as they are both under warranty and hopefully I can get to all the oil changes on everything else. I replaced the water pump this morning.

[old Rusty C10]

well im glad you got it licked hopefully the MIL will be happy!