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Basic brake problem killing me!

SouthernXJ

NAXJA Forum User
Location
South Carolina
Ok, so to save some money I dont have, I decided to replace my wife's rotors and pads on her 99 XJ. I cant get into my bud's garage, so it's done in the driveway. No light at all, knuckes busted all to heck and back, but I get them on and bled. Now, my problem.

The pads are squeezing the rotors (without pushing the pedal) and I cant even move the Jeep. I must have done something wrong, but I'll be darned if I can figure out what it is.

Any suggestions?
 
When you changed the pads, did you confirm that the calipers were sliding freely on the pins?

What I would try is open the bleeder on one caliper, then use a screwdriver or small-ish pry bar to press the caliper away from the rotor. Some fluid will squirt out of the bleeder, but if you shut it quickly after the spurt it shouldn't let any air in.

If that frees up one side, repeat on the other side.
 
Cool, I'll try that tomorrow. I am beat to a pulp now. Man I hate brakework!

No, I didnt know to check that. Darn you Haynes manual!!!

Thanks for the idea!
 
Not so much a problem with Jeep. But on other manufactures disc brake pistons. The pistons sometimes rust up or become plugged with junk around the piston/rubber seal. The worn pads allow, the extended piston to seat in this possition. The new pads, make the piston work in a more closed position and it sometimes sticks some. A good cleaning, toothbrush and mild soap or in extreme cases a spray oil, often helps.
Crack the bleeder and push the piston all the way in. A "C" clamp and a piece of wood works. Kind of hard to find a level spot on the back of the piston housing, for the C clamp, but it´s doable. I have a really large (like 18") set of channel lock pliers I use. Be careful of the brake lines, flexing them in odd ways or hanging the piston assembly by them, causes cracks in the rubber brake lines.
If the rubber boot around the piston is torn, chances are there is rust and water in with with the piston. Not much chance of saving a internally rusted piston and housing.
Usually one side or the other sticks. A slight rub, between the pads and disc, doesn´t mean much. If you can turn the disc by hand and there is no significant resistance, chances are it will wear in OK. If it turns with a minor resistance, keep an eye on it. Overheating can damage the disc and glaze the pads.
There are plasic inserts in the part of the piston assembly (caliper), that rides on the rods, if these become twisted or have slipped, this can cause the piston assembly (caliper) to not center properly. Will cause uneven pad wear and sometimes sticking.
There are other things that can cause sticking or hanging piston/calipers, but these are the most common.
 
iv also seen the rubber hose close in on themself and act like a check valve holding the piston tight can happen after letting the caliper hang from the hose when they get old (nobody does that right lol )
 
massxj said:
iv also seen the rubber hose close in on themself and act like a check valve holding the piston tight can happen after letting the caliper hang from the hose when they get old (nobody does that right lol )

Isn't that why dry cleaners give you all those wire coat hangers when you get your clothes back?
 
iv also seen the rubber hose close in on themself and act like a check valve holding the piston tight can happen after letting the caliper hang from the hose when they get old (nobody does that right lol )

What's the solution for that? I did let them both hang not knowing any better. :(

8Mud, thanks for the reply. I dont think it's the piston because it moved pretty easily when I separated the pads to fit it on the rotor.
 
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SouthernXJ said:
What's the solution for that? I did let them both hang not knowing any better. :(

8Mud, thanks for the reply. I dont think it's the piston because it moved pretty easily when I separated the pads to fit it on the rotor.

The best solution is new hoses. Sometimes what happens is that the hose deteriorates inside and forms a sort of flap that acts like a valve.

If you got the pads over the rotor easily enough without forcing, the piston must have been retracted enough to start with. The next question is, are you sure you got the right rotors? Are you sure it's the pads holding the rotor now, or could it be some other interference?
 
see if you can compress the piston with the hose on if you can its not the hose .if you cant open the bleeder and try againif .it works it the hose or somthingin between the caliper and the master is bad if you open the bleeder an the piston will not move it the caliper
 
Could be the brake lines collapsing, though I´ve never run across it myself. The brake lines are made in layers, the inside layer is often pretty soft.
The pistons retract very little and there really isn´t much in the way of suction to help. Very little binding will cause enough friction to lock up the pads/disc.
I´d work the piston in and out a few times, exercise it and see if this doesn´t help. Then I´d fill a small glass jar with an inch of brake fluid, run a piece of plastic windshield washer tubing into the fluid it the jar (so the tubing can´t suck any air). Do a couple of rounds of pedal, close bleeder, open bleeder, then leave the bleeder open (slightly) when your sure the plastic line is full of fluid. Add fluid as you pump it down, until clear fluid comes through. Clear plastic aquarium tubing works best, you can look and make sure there are no air bubbles in the line.
The thing that throws me, is that as I understand it, both are locking up. There are very few things both sides have in common. The master cylinder is one. I´ve seriously bleed brakes before and have gotten an amazing amount of crude out of the system. Not gonna state an oppinion as fact, but it seems possible a check valve or orifice in the master cylinder may be plugged with crud.
Have had pads that were too thick from the manufacturer, took a little sanding to get them to work. Have had moisture in the system that made steam at operating temps. and locked the brakes down. Have had pistons stick. Have heard of collapsing rubber brake lines causing binding, crud in the master cylinder, bent caliper rods and flattened hard lines causeing binding (enough pressure to force through fluid, but not enough pressure/suction on the return, to allow the pistons to retract). In theory a pinched rubber brake line could do the same thing as a pinched hard line.
Had one set of brakes that hung up, drove me nuts, until I noticed the star retainer for the disc, was on the inside and making the discs/pads seat crooked. Don´t ask me why the last mech. put the retainers on the wrong side of the disc. It´s usually something simple.
 
A real longshot, but worth a look, check and see if the pad is sitting level on the piston rim. Some brake pads look identical, to pads designed for use on calipers with a bigger piston. The only difference is on the back of the pad backing plate. They sometimes sit a little crooked, hard to notice.
 
I'll print all that out for future problem solving, but I figured it out.

PepBoys (my first problem) gave me the wrong rotors. Their computer had them listed as the right ones, but they were a little too deep. The extra depth was causing the rotor to bind with the backing plate of the hub. Then, when I put the lugs on, it really smashed everything together and the wheel couldent be turned. So, 3 parts places later, I find the right rotors (at only $19 a pop!) and it stops like new :)

Thanks for all the suggestions, guys! I'll definatly keep all those suggestions in mind next time I run into a similar problem, which for me, problems come often!
 
Sorry I was so windy, seen the wrong rotor problem before, the middle of last summer. I´ll move that one up, on my list of possibilities.
Was a resident Mech. for an auto hobby shop for years (night job). Have seen a lot of strange things, wrong parts and wrong reference material.
Murphy´s law. Anything that can go wrong, will go wrong.
Or one of my favorites. Faster than the engineers can produce a fool proof machine, God produces a better fool. I´ve really seen some strange things at the shop.
Personal. First time a mistake, second time foolish third time :doh:
 
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