Kama

I recently did a brake power booster upgrade to my '91 XJ. I pulled one from the junk yard from a '97. Yesterday and today after driving, the pedal gradually started to not go down as far and got to the point where I barely had to touch it to stop. The rotors were very hot on both front wheels and I'm not sure what the smell was but it was definitely coming from the area around the pads. Most likely the pads from not being released? I searched the forums but nothing really fits.

At first I was thinking the caliper, because the driver side was squeeking like it wasn't retracking all of the way but now since both sides are hot, I'm not sure.

Plenty of brake fluid too.

Any ideas?

Thanks guys.

outkast

I doubt its your master cylinder if you calipers are not releasing. My guess would be that when you put the master on the "upgraded" booster the rod was to long and is holding the pressure on the master.

Kama

It's been working fine for about a month now. Is it possible for it to all of a sudden start being an issue?

Could the new booster cause both calipers to fail?

xj101

first off i would scope them calipers and lube em up , its easy. just my .02

Kama

I went out this morning and lubed everything. After the test drive, the driver side didn't shown any issues, but the passenger side did. The boots for the pins on both are shot. I'm leaning towards overhauling the calipers.

I noticed that the place where the pads slide are not as smooth as I think they should be. Does any one know if it is ok to take a file to the area to make it smooth again? I can see how that would keep the pads from sliding.

Probably not going to get a lot done today. Lots of eating to do. Trying to convince my family that we should have roasted rabbit for Easter. So far I'm the only one who thinks that this would be a good tradition to start.

Thanks for your help.

outkast

Your on the right track. When I read your post I was thinking you started having problems right after the swap.

Kama

Here's what I discovered:
I was thinking that it was the flexible brake line, but because both fronts were locking up, I started with the master cylinder. The chances of the lines going bad on both at the same time is pretty small. As soon as I took the lines off the master, both pistons released.

I was told that sometimes the inside of the brake line will deteriorate and start to act like a check valve.

I was also told that the master has a port that allows the fluid to come back into the cylinder to release the piston. That sometimes the seal will swell up which causes the port to be block because it doesn't come back all the way. The swelling can happen from moisture getting in the fluid. I got the booster and master cylinder at the junkyard and for some reason they don't put the caps back on after they drain the fluid.

Thanks for your feedback guys. I hope this helps someone else down the road.

Kama

I thought that it was fixed, but on the way back from the junkyard this morning the driver side locked up. It was smoking like crazy. After I stopped and let it cool down some, it drove good again. The pedal doesn't have as much travel as it use too. If I press hard on the pedal the brake light comes on too and stays on until I turn the engine off, start it back up a press down a little.

I was reading in the haynes that while bleeding the brakes I should have had the igition switch on. Could that be what is causing this? Does anyone know what that does anyway?

Any ideas? This is my DD and I've been driving around in a car that is not quite legit. It just a matter of time before I get busted for it.

Thanks.

freegdr

brake basicshttp://mysite.verizon.net/vzep121w/r...stop/id17.html

freegdr

what did you replace anthing yet

Kama

Thanks for the link.

I replaced the master cylinder and changed the fluid from DOT 3 to DOT 4. The instructions with the master said too.

freegdr

did the master go all the way down onto the bosster flush by hand?

outkast

The point to having the key on while bleeding the brakes is so the ABS can actuate. If you don't have ABS there is no need to worry about it.

freegdr

starting to seem like brake lines/calipers are going out heresanother linkhttp://auto.howstuffworks.com/auto-p...ake-hoses2.htm

Kama

I didn't try to tighten the master onto the booster by hand. One of the things I was thinking is if the adjustment rod on the booster might need to be backed off.

All of the "locking brakes" paragraphs suggest the rear brakes or the parking brake.

I started off with the hoses and calipers, but the problem solving that was suggested didn't work, so I didn't install them. Once I loosen the master cylinder, both of the calipers released. I returned everything except the master.