brake issue

[dndeans]

Help. I'm having an issue with my rear brakes that I've not seen posted. My ABS light has been on now for about a year. At first this was not a problem or so I thought. Brakes acting normal but new pads were needed so I replaced them all around. About two months later my daughter was driving it to school across the state, and called to say she was having brake problems. Mechanic at her location said that the brakes were shot. He installed new calipers and rotors on rear and pads all around. About one month later daughter reports intermittent noise and a mechanic in her area sees no problem with her brakes. One month later and the daughter is home and still having intermittent problems. I check brakes to find inner pad on right rear completely worn out and rotor worn. When I tried to push the caliper piston back in it was very stiff. At first it moved ok but then stiffened up as if the return line was plugged. Is it likely that my abs system (with the fuse out) is valving off the return brake line? Does the abs module referred to in previous post include the valving or is it just the electrical part? Any other suggestions to fix this not so intermittent problem now?

[SlowPro48]

Had this happen on my truck a few years ago. Took a while to figure it out. Turned out to be the brake line. They have two layers and the inner layer developed a tear. The resulting flap of rubber acted as a check valve that prevented brake fluid from flowing back out of the caliper when I let off the brakes, so that one caliper was dragging all the time. Might want to replace the brake line and see if that helps.

[VxSport]

Just a quick thought.... check the slider pins on the Calipers too.... I know your mechanic should have greased them too.
I wonder if you could check the brake lines with Vac pump on each end of the brake line.... to see if it won't flo both ways evenly.
keep us informed

[chadzu]

when I bought my vx this summer I went over the brakes first thing. I found that 3 of the 4 calipers had badly corroded pins, and one rear actually had a pin broken off and was just being held on by a little stub. I replaced all the pins and the caliper brackets with good used trooper parts and it make a big difference.
I think many times a mechanic only pulls the bottom pin and rotates the caliper up to insert new pads. This can lead to seizure because they never get properly cleaned and greased.

[tom4bren]

X2 on what they said.

It's the opportune time to upgrade to Stainless Steel brake lines & a GOOD brake job. The SS brake lines are probably going to be cheaper than OEM so that's a no-brainer. You'll lose all of your brake fluid during the install of new lines ... but that's a good thing. If your brake lines have been compromised, the fluid may be contaminated. Just be fore-warned, bleeding your brakes after refilling is CRITICAL and difficult by yourself. Plan on having a helper available for that part. While you are in the process of replacing the pads, you'll see what parts have to be able to slide & which ones are stationary. Anything that slides should be cleaned and lubricated.

If your rotor is scored & is too far gone to just be turned, you may want to check into cross drilled rotors. Rumor has it that it can improve the braking performance (I'm still running the original rotors so I can't verify that for you).

There are plenty of threads on SS brake lines & cross drilled rotors so use the search function on the home page to find them. It'll help save you quite a bit of on line research trying to source parts. Additionally, the better informed you are, the better you'll be able to work with your mechanic in the future to diagnose the issue.

[dndeans]

All moving parts are in great shape and slide easily. Caliper piston won't fully retract. The vacuum pump test sounds promising for checking the hoses. Do I connect to the bleed valve to extend the piston, then remove the hose and apply vacuum to the end of the hose? I would think that if upon removing the hose, the piston would still resist moving would be an indication that the hose was bad. If on the other hand the piston moved freely, that would indicate that the problem was further upstream than that hose. I've been reading the workshop manual and found that the master cylinder could be a suspect. I'll probably start by changing the hoses first anyway. Does anyone think that the abs control unit could be the problem?

[tom4bren]

Does anyone think that the abs control unit could be the problem?

Not likely ... but anything is possible.

ABS modules are intentionally designed to NOT degrade braking performance if the unit fails.

My best guess is that you have a bad caliper. Second choice would be the lines (solely based on post #2). Master cylendar isn't high on my probability list since it serves all 4 brakes & only 1 is affected.