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Unread 07-07-2013, 01:11 PM   #1
jahill
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Calipers won't open up after replacement

I've been looking and looking on here, and I can't seem to find exactly what to do.

I decided to do a complete brake replacement. Bought this '99 Cherokee Sport used, it has 175k on it, and they were starting to squeal on me. Replaced the rotors, calipers, and pads.

Rotors are correct. I compared them to the ones I took off, and they are the same dimensions (I saw where they were changed halfway through '99).

Calipers are on correctly; bleeder screws are on the top.

I've bled the brakes, going from RR to LF... did both gravity feed and the brake pumping, finally getting the pedal not to be squishy when the engine was turned on. Reservoir did not get more than half empty.

But now, the calipers are stuck closed.

I know I can just take them off, push them back in, and then set them back on, but I'm afraid that they'll close and not open back up (again).

I can't see it being the master cylinder, because it was fine before I did this work. I also can't see it being a collapsed line since it gravity bleeds just fine.

Ideas?

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Unread 07-07-2013, 01:17 PM   #2
98muddyjeep
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What do you mean they are stuck closed? The piston doesn't retract fully when their is no pressure on them they jut sit their till you apply pressure and then they pinch the pad till you stop.
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Unread 07-07-2013, 01:21 PM   #3
jahill
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Sorry, I mean that the piston is out, pushing the pads against the rotors. All this while no pressure is put on the brake pedal. Pushing on the brake pedal to try and cycle the cylinder produces no effect: they do not retract. Trying to get the Jeep to move at all in drive or reverse does nothing; the Jeep just sits there as if I still had my foot on the pedal.
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Unread 07-07-2013, 01:31 PM   #4
CJ7-Tim
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Even though you are aware of the 99 brake rotor types, that you might have the wrong rotors would be the first thing to suspect. If removing the tire allows the rotor to spin, you have the wrong rotors.

Anytime I replace calipers, I also replace the rubber hoses. The hoses can breakdown internally, causing a blockage the defeats return flow of brake fluid when the brake pedal is released.
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Unread 07-07-2013, 01:38 PM   #5
jahill
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I agree that the rotors would be the first thought for me, if it weren't for the following:

1) When the caliper is not extended (i.e. inside the housing all the way), the pads are not pressed against the rotor.
2) The two types of rotors I've seen for '99 seem to have one major difference: a little edge/"lip" on the part of the rotor that sits over the five bolts. And when I held the two rotors up to each other before I took anything else off, they matched up.

Any way to tell if it is the hoses or not? Like I said, they gravity bleed just fine. I'm really not wanting to have to bleed the system again because I had so much issue with it (pedal would harden up when depressed with engine off, but then would go all the way to the floor when engine was turned on. Finally got it firmed up, but took a LONG time and a LOT of brake fluid).
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Unread 07-07-2013, 01:43 PM   #6
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See this thread - http://www.jeepforum.com/forum/f11/a...e-hubs-360959/ - and confirm you have the correct rotors.

Faulty rubber hoses stop the return flow of brake fluid, keeping pressure on the calipers. New hoses are inexpensive and worth the investment.
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Unread 07-07-2013, 01:47 PM   #7
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In order for the pressure to release the brake pedal must return to it's resting position, along with the shaft which moves the piston in the master cylinder. This opens up a non restricted passage for brake fluid to return to the reservoir. Did you adjust this? Or, did it fall out of position when you removed the calipers? Crawl up under the dash and pull the brake pedal back and see if it's all lined up correctly.
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Unread 07-07-2013, 02:01 PM   #8
CJ7-Tim
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Quote:
Originally Posted by Diamond-x View Post
In order for the pressure to release the brake pedal must return to it's resting position, along with the shaft which moves the piston in the master cylinder. This opens up a non restricted passage for brake fluid to return to the reservoir. Did you adjust this? Or, did it fall out of position when you removed the calipers? Crawl up under the dash and pull the brake pedal back and see if it's all lined up correctly.
I disagree with this theory. The brake pedal needs no adjustment or inspection when simply changing the calipers.

The most logical cause of the problem still is incorrect rotors.
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Unread 07-07-2013, 02:25 PM   #9
jahill
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Tim,

Just measured the rotors I took off with the new ones. The actual rotor part is 15/16" (roughly) on both, and (including the "hub" part) 3 3/16" total. According to the link provided, they are composite rotors. But, according to the measurement of the hub bolts, I should have the cast rotors.

Hmmm... so apparently, I have the cast iron bolts but had composite rotors on there. Any idea how they would have worked to begin with? Guess I'll head to Autozone now and see if they have the cast rotors. Weird.

Sorry, I just looked at the rotors, not the hub bolts.

EDIT: OK, this is what I get for trying to hurry and being irritable from having worked on this since yesterday afternoon. The bolt measures 1 1/2" while the "hub" is 3/4", which means composite rotors are correct. Also, removing the tire does NOT allow the rotor to spin; again, the pads are still pressed down on the rotor so that it won't spin.

Last edited by jahill; 07-07-2013 at 02:42 PM..
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Unread 07-08-2013, 06:58 AM   #10
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The only time this ever happened to me was when the piston got stuck in the master cylinder on an old K5 Blazer. But all 4 brakes stayed locked up instead of just the fronts.
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Unread 07-08-2013, 06:06 PM   #11
jahill
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Tim: Going to try replacing the break lines. Here's hoping.

foggybottombob: Short of replacing the master cylinder, how'd you get the piston unstuck?

EDIT: Not quite sure if all the brakes are locked up or it's just the front disc calipers. Never dealt with drum brakes before, so not sure what I'd be looking for that would say, "Hey, we're locked up, too!"
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Unread 07-08-2013, 06:10 PM   #12
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If you take the brake caliper off how easy does the piston push back into the caliper? With new calipers it should be fairly easy to push them back in you can also Try clamping the rubber line and open the bleeder valve and push the piston in, if it goes in fine when you bypass the line this way as Tim suggested I would look at New hoses.
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Unread 07-08-2013, 06:12 PM   #13
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Where ya located at maybe if you reach out o a local member you may get a second opinion
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Unread 07-08-2013, 06:50 PM   #14
blackolive99
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I second the replacement of the rubber lines.
Step on the brake. Release. Wheel stuck? Open bleeder and wheel spins? Replace the lines. Worked on my neighbors little buggy and after master cyl, and four drum cly, the fix was rubber hoses. All four ( it was a vw buggy) i know not a jeep, but it sounds likr the same problem.
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Unread 07-08-2013, 07:52 PM   #15
jahill
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Haven't tried releasing the bleeder yet. Figured I'd just go ahead and try the lines, but I will tell you that trying to push the caliper in while it was still attached to the line was difficult. Had to use a c-clamp with a piece of wood on the caliper to get it to close. It did push the fluid back up into the reservoir, but if there is a blockage, I don't want to do it too often or to the other side and get the blockage back up in the system somewhere. Just seems a bit... strange... that BOTH lines would have this problem.

Also, after pushing the caliper back in, it isn't as tight on the rotor after I press on the pedal. I do get some spin, but if I try driving the vehicle around, all I hear is the scraping of the pads and rotors on each other.

As for reaching out to a local person, there's a guy in my electrician's class that's a Jeep guy, so I'll run it by him tomorrow night.

I was able to get one line replaced tonight, but then ran into the problem that the parts store gave me two passenger side lines rather than one driver/one passenger. Lovely. Of course I don't find this out till it's too late to hit any other store tonight, which means Saturday can't come soon enough to where I have time to work on the other line.
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