Help, stuck in middle of rear brake job

[jnaut]

Am trying to compress rear (passenger side) caliper piston down far enough to get new pads over rotor, and I can't physically compress piston down far enough. Bottom pad goes on, but top pad won't go on with enough space between them to slide over rotor.

I have literally destoyed one very large C-Clamp trying to get piston compressed. Is there something I'm doing wrong, or is that a sign the rear caliper needs to be replaced. Can't drive truck until this gets solved.

Any help appreciated.

 

[TAwesome]

I know it might sound dumb but you removed the reservoir cap right?

 

[TAwesome]

oh wow wait rear piston those usually turn in! You can do this with needle nose plier. But your best bet is to borrow the compressor tool from your local autozone.

 

[ptsb5a]

jnaut, crack the bleed screw open a bit and compress the piston, see if that helps. Giving the brake fuild a place to go might help with the piston issue.

I don't know if the KJ has residual pressure valves in the brake system. Usually 2-3 psi for disc brakes. If there is, one may be stuck.

 

[jnaut]

Yes, res cap is off. What do you mean 'turn in'? Book says compress with large c-clamp. I got it compressed most of the way, but the last little bit took all my strength, ended up bending the C-clamp all out of whack. It ain't gonna compress any more without something like a hydrolic bottle jack jerry-rigged to it. I have no idea what the eff I'm gonna do, beyond put the old brake/rotor back on. I'm seriously suspecting a bad caliper.

 

[jnaut]

jnaut, crack the bleed screw open a bit and compress the piston, see if that helps. Giving the brake fuild a place to go might help with the piston issue.

I don't know if the KJ has residual pressure valves in the brake system. Usually 2-3 psi for disc brakes. If there is, one may be stuck.

Ok, where the bleed screw at? I'll go out and look at my book while I await your answer.

 

[TAwesome]

Yes, res cap is off. What do you mean 'turn in'? Book says compress with large c-clamp. I got it compressed most of the way, but the last little bit took all my strength, ended up bending the C-clamp all out of whack. It ain't gonna compress any more without something like a hydrolic bottle jack jerry-rigged to it. I have no idea what the eff I'm gonna do, beyond put the old brake/rotor back on.

So you were able to compress is most of the way. Ok then ignore my last statement. Some rear pistons are solid and require being turned like a screw but if you have a hollow piston it is meant to be compressed not screwed.

http://www.ehow.com/how_5828458_compress-piston-rear-disc-brakes.html

 

[ptsb5a]

oh wow wait rear piston those usually turn in! You can do this with needle nose plier. But your best bet is to borrow the compressor tool from your local autozone.

Pistons turn in when they are also used as the park brake. kind of a self adjusting feature. The KJ has tiny drum brake shoes in the hub that act as a park brake. They press out against the wee drum that is an integral part of the rotor.

 

[ptsb5a]

Ok, where the bleed screw at? I'll go out and look at my book while I await your answer.

The bleed screw is on the caliper. It'll be at the highest point of the fluid resevoir part of the caliper. It's used to let air out of the system when perfroming a brake bleeding. Might still have a tiny rubber cap on it.

 

[TAwesome]

Brake job has not reached the top of my list of to do's yet. Please accept my apology just using my knowledge from other vehicles I have owned.

 

[jnaut]

No prob, TAwesome.

ptsb5a: there's a little rubber nipple right above the 'banjo' bolt (what the rubber brake line connects to) right on the caliper, could that be it? I'll try to snap a picture and post it in a sec...

 

[ptsb5a]

That'd be it. Take the rubber nipple off. It's mearly a dust boot and keeps the brake bleed screw free of stuff that would otherwise plug the hole through which brake fluid would flow.

 

[TAwesome]

One other thing is making sure that it didnt get compressed on an angle and jam. If so that is a mostly easy fix. Press on brake pedal should loosen it.

 

[jnaut]

Ok, just for verification, this is what you're talking about?

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[TAwesome]

Just to speed things up for you yes that is what he is talking about!

 

[TAwesome]

Yeah don't be afraid to pull that off you will see the screw easily after it is removed!

 

[ptsb5a]

Ok, just for verification, this is what you're talking about?

You must be registered for see images attach

Yep. Now take the little rubber cap off. Use the appropriately sized six point deep socket on it or a flare nut wrench if you have one and loosen it off just enough to get brake fluid to flow out. Push the piston into the bore and close the bleed screw before air can have a chance to get in. If you do get air in there your brakes will feel a wee bit spongy. then you need either a buddy or a SWMBO to help out with the bleeding..

 

[TAwesome]

Hoping your gap in time is a good sign. Maybe putting pads on and don't have time to reply!!

 

[jnaut]

Yep, did that. No dice. Thought that was a cool suggestion, too. That piston won't budge. This is as far as I can get it compressed. As soon as I put the outside pad on, there's no where near enough room to get it over the rotor. Any other thoughts?

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[TAwesome]

My only other suggestion is use two clamps to make sure your evenly compressing. And if your not already use the old pad as a platform.