LOST JEEPS :: View topic - HELP! rear disc brake frozen

Oh, before that, I stepped on the brake pedal and the piston moved out slowly and seemingly smoothly. But now I can't get it back in.

The piston is made from a phenolic resin (plastic
material) and should be smooth and clean.
The piston must be replaced if cracked or scored.
Do not attempt to restore a scored piston surface by
sanding or polishing.

BRAKE DRAG
Brake drag occurs when the lining is in constant
contact with the rotor or drum. Drag can occur at one
wheel, all wheels, fronts only, or rears only.
Drag is a product of incomplete brake shoe release.
Drag can be minor or severe enough to overheat the
linings, rotors and drums.
Minor drag will usually cause slight surface charring
of the lining. It can also generate hard spots in
rotors and drums from the overheat-cool down process.
In most cases, the rotors, drums, wheels and
tires are quite warm to the touch after the vehicle is
stopped.
Severe drag can char the brake lining all the way
through. It can also distort and score rotors and
drums to the point of replacement. The wheels, tires
and brake components will be extremely hot. In
severe cases, the lining may generate smoke as it
chars from overheating.
Common causes of brake drag are:
† Seized or improperly adjusted parking brake
cables.
† Loose/worn wheel bearing.
† Seized caliper or wheel cylinder piston.
† Caliper binding on corroded bushings or rusted
slide surfaces.
† Loose caliper mounting.
† Drum brake shoes binding on worn/damaged
support plates.
† Mis-assembled components.

STANDARD PROCEDURE - MANUAL BLEEDING
Use Mopar brake fluid, or an equivalent quality
fluid meeting SAE J1703-F and DOT 3 standards
only. Use fresh, clean fluid from a sealed container at
all times.
Do not pump the brake pedal at any time while
bleeding. Air in the system will be compressed into
small bubbles that are distributed throughout the
hydraulic system. This will make additional bleeding
operations necessary.
Do not allow the master cylinder to run out of fluid
during bleed operations. An empty cylinder will allow
additional air to be drawn into the system. Check the
cylinder fluid level frequently and add fluid as
needed.
Bleed only one brake component at a time in the
following sequence:
† Master Cylinder
† Combination Valve
† Right Rear Wheel
† Left Rear Wheel
† Right Front Wheel
† Left Front Wheel
(1) Remove reservoir filler caps and fill reservoir.
(2) If calipers, or wheel cylinders were overhauled,
open all caliper and wheel cylinder bleed screws.
Then close each bleed screw as fluid starts to drip
from it. Top off master cylinder reservoir once more
before proceeding.
(3) Attach one end of bleed hose to bleed screw
and insert opposite end in glass container partially
filled with brake fluid (Fig. 1). Be sure end of bleed
hose is immersed in fluid.
(4) Open up bleeder, then have a helper press
down the brake pedal. Once the pedal is down close
the bleeder. Repeat bleeding until fluid stream is
clear and free of bubbles. Then move to the next
wheel.

Author:	AdamIsAdam [ Fri Jun 23, 2006 7:38 pm ]
Post subject:	HELP! rear disc brake frozen - BRAND NEW!
Help! My BRAND NEW set of rear brakes (new rotors & pads) is frozen (left rear only). My mechanic went home for the weekend of course. I've done brakes and have a shop manual, but not for years. What I'd like to do is just get it freed up so I can drive it this weekend without the smoke I've currently got! My rotor has already turned blue on the inside and outside edges of the contact area, so I'll be getting a new rotor come Monday. but what's the best way to try and free it up without taking the whole thing apart? And if I do, what's the proceedure? I'm reading the manual and it basically says pry the piston in and take off clips and caliper. Assuming I do that, how do I know it's not going to freeze right back up again? I tapped the caliper lightly with a hammer hoping something would let go, but that didnt' do anything. The right rear is fine. The parking brake is fine and functional. It's definitely the disc brake. Help!!! tnx

Author:	AdamIsAdam [ Fri Jun 23, 2006 8:07 pm ]
Post subject:
Well, I manged to get a screwdriver (not a great idea, I now) between the piston and pad and pry it back slightly. just enough to allow the disc to spin freely again. There seemed to be some dirt around the piston area. I sprayed it with compressed air. I stepped on the brak pedal and it's locked up again. Now what. I guess I need to take the whole assembly apart, clean it out? Someone please write up some tips here for me. Also, can I only spray brake cleaner on brakes? (which I'm out of!!!) or can I spray wd40 or silicone?

Author:	tjkj2002 [ Fri Jun 23, 2006 8:09 pm ]
Post subject:
Are the rear caliphers brand new or remanufactured?If they are new they may have some crud(from the port for the line being open)or have some corrosion between the housing and piston.If they are remanufactured ones then the same thing goes or they put them together wrong.It is possible also your mechanic could have compressed the piston unevenally and the piston could be jammed at a angle,try prying the piston back in(very carefully,and by the pad,do not pry on the piston)and then see if they lock again.Most likely you will need a new caliper also and a good brake flush to make sure no crud is left in the lines if any was present.Also you can check the lines for kinks,maybe metal line on to tight and crushed the double flair to far and the fliud can't go back to the master cylinder.Just my 2 cents,hope it's not to badly damaged.

Author:	Mutt [ Fri Jun 23, 2006 8:13 pm ]
Post subject:
My guess is that the piston is stuck in the bore. Take the caliper off, remove the pad,visually inspect to see if piston looks cocked, open the bleeder, and try to push the piston all the way in. It's hard to guess without being there.

Author:	tjkj2002 [ Fri Jun 23, 2006 8:17 pm ]
Post subject:
Mutt is probally right,with caliper off you should be able to turn the piston in its bore(it shouldn't turn real easy though).

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HELP! rear disc brake frozen - BRAND NEW! http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=1&t=9738	Page 1 of 2

Author:	AdamIsAdam [ Fri Jun 23, 2006 8:24 pm ]
Post subject:
I'm going to pep boys for brake cleaner. The calipers are old. the discs and pads are new. No kinks appear in lines. I'm guessing dirt was around the piston and when he compressed it, he send the dirt in there too!

Author:	AdamIsAdam [ Fri Jun 23, 2006 9:18 pm ]
Post subject:
ok, what am i missing here? I've gvot the caliper off. The brake pads won't come off. I guess I have to slide the outter pad off first but it's on there SO tightly that I can't get it off. And I've got the hose connected so I've got limited room. I tried to push the pads apart more by placing stuff in the slot where the disc would go and it doesnt' seem to be moving the piston in at all. I sprayed the whole area with brake cleaner. Should I be able to step on the brake pedal a little to make the piston come out some, then clean it, and push it back in more?

Author:	Mutt [ Fri Jun 23, 2006 9:19 pm ]
Post subject:
Did you open the bleeder?

Author:	AdamIsAdam [ Fri Jun 23, 2006 9:23 pm ]
Post subject:
no. oops. It's been a long time, as I said. I'm trying to avoid needing to bleed the system so I wasnt' thinking. be right back!

Author:	AdamIsAdam [ Fri Jun 23, 2006 9:44 pm ]
Post subject:
Now I remember why I hate doing brakes! How do I compress the piston back in? I opened the bleeder just enough to let some fluid drip out. I put some c clamps on the pad's center, and the other end on the back of the caliper and I can barely get it to move. Oh, before that, I stepped on the brake pedal and the piston moved out slowly and seemingly smoothly. But now I can't get it back in. I have the cap off the fluid resevoir. I keep closing the bleeder for fear of taking in air. HELP! The manual just says put htem back on. Thanks!

Author:	Cacher123 [ Fri Jun 23, 2006 9:50 pm ]
Post subject:
Sounds like u need to rebuild that caliper. I don't know if there are any seals in there (I've worked on many a motorcycle brake assy and there is usually one seal or oring) but if there is it's probably damaged from whatever dirt got in there. Unless u release the bleeder, I doubt you'll get the piston back in. If u r worried about sucking air in, place a length of clear tubing, with a diameter that fits tightly over the bleeder, over the bleeder and stick the other end in a bottle of brake fluid (after filling the tube with fluid) so all you'll suck back in is more fluid. If u do rebuild the caliber you may need to clean up the bore as well as the piston with some emery cloth and replace the seal. Quote: Oh, before that, I stepped on the brake pedal and the piston moved out slowly and seemingly smoothly. But now I can't get it back in. I was gonna reply and tell u not to do that but too late! Edit: According to my service man., there is a seal as well as a dust boot. Quote: The piston is made from a phenolic resin (plastic material) and should be smooth and clean. The piston must be replaced if cracked or scored. Do not attempt to restore a scored piston surface by sanding or polishing. From the service man. Seems like my earlier thought about resurfacing the piston is wrong. Sorry!

Author:	Mutt [ Fri Jun 23, 2006 10:04 pm ]
Post subject:
Dude, if you want the piston to travel back, leave the bleeder open and press it back. Put a rag around the bleeder if you're worried about making a mess. I've seen brake pistons that were cocked and didn't have a problem coming out. They just wouldn't retract into the bore. Sorry, could be more help if I could "lay hands on it." "Dearly beloved, we call upon an incantation to fix poor Adam's recently repaired brakes."

Author:	AdamIsAdam [ Fri Jun 23, 2006 10:07 pm ]
Post subject:
I finally reassembled everything. I was able to get the piston back in by putting the assembled caliper back onto the rotor. I got everything together. I sprayed everything that I could see with brake cleaner. It spun freely... until I stepped on the brakes. Now it's seized again. I guess I'll take the caliper apart and see if I can clean it out. But based on what the manual says, I'll be needing a new caliper, no? Also, what's the best way to deal with the brake line to minimize air in the system? I'll be removing the line from the caliper to work on my bench with it. (I tried the line into a tube-cup of brake fluid but i didn't have the right sized hose. oh well.)

Author:	AdamIsAdam [ Fri Jun 23, 2006 10:09 pm ]
Post subject:
feel free: 516-443-1053

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Author:	Cacher123 [ Fri Jun 23, 2006 10:11 pm ]
Post subject:
Tried to send u the serv man but the file is too big.... I guess u don't have a brake vacuum pump? Quote: BRAKE DRAG Brake drag occurs when the lining is in constant contact with the rotor or drum. Drag can occur at one wheel, all wheels, fronts only, or rears only. Drag is a product of incomplete brake shoe release. Drag can be minor or severe enough to overheat the linings, rotors and drums. Minor drag will usually cause slight surface charring of the lining. It can also generate hard spots in rotors and drums from the overheat-cool down process. In most cases, the rotors, drums, wheels and tires are quite warm to the touch after the vehicle is stopped. Severe drag can char the brake lining all the way through. It can also distort and score rotors and drums to the point of replacement. The wheels, tires and brake components will be extremely hot. In severe cases, the lining may generate smoke as it chars from overheating. Common causes of brake drag are: † Seized or improperly adjusted parking brake cables. † Loose/worn wheel bearing. † Seized caliper or wheel cylinder piston. † Caliper binding on corroded bushings or rusted slide surfaces. † Loose caliper mounting. † Drum brake shoes binding on worn/damaged support plates. † Mis-assembled components.

Author:	Cacher123 [ Fri Jun 23, 2006 10:18 pm ]
Post subject:
Quote: STANDARD PROCEDURE - MANUAL BLEEDING Use Mopar brake fluid, or an equivalent quality fluid meeting SAE J1703-F and DOT 3 standards only. Use fresh, clean fluid from a sealed container at all times. Do not pump the brake pedal at any time while bleeding. Air in the system will be compressed into small bubbles that are distributed throughout the hydraulic system. This will make additional bleeding operations necessary. Do not allow the master cylinder to run out of fluid during bleed operations. An empty cylinder will allow additional air to be drawn into the system. Check the cylinder fluid level frequently and add fluid as needed. Bleed only one brake component at a time in the following sequence: † Master Cylinder † Combination Valve † Right Rear Wheel † Left Rear Wheel † Right Front Wheel † Left Front Wheel (1) Remove reservoir filler caps and fill reservoir. (2) If calipers, or wheel cylinders were overhauled, open all caliper and wheel cylinder bleed screws. Then close each bleed screw as fluid starts to drip from it. Top off master cylinder reservoir once more before proceeding. (3) Attach one end of bleed hose to bleed screw and insert opposite end in glass container partially filled with brake fluid (Fig. 1). Be sure end of bleed hose is immersed in fluid. (4) Open up bleeder, then have a helper press down the brake pedal. Once the pedal is down close the bleeder. Repeat bleeding until fluid stream is clear and free of bubbles. Then move to the next wheel.

Author:	AdamIsAdam [ Fri Jun 23, 2006 10:23 pm ]
Post subject:
I've got the manual, thanks. I see that there's no point in trying to rebuild the caliper since I should be using new seals and also should have a press tool to get the piston back in. Since I'm going to demand new pads and a rotor on that wheel anyway, I'll just deal with it over the weekend and try not to drive it. Not sure that's goign to work, but i"ll try. Maybe I'll catch my mechanic tomorrow if he goes in. not likely, but I'll try. Or, I'll just buy a new caliper tomorrow and do it myself, then demand new pads and rotor while I make him power bleed the system next week!

Author:	Cacher123 [ Fri Jun 23, 2006 10:29 pm ]
Post subject:
If u r going to replace it anyway, I'd try to clean it up best as possible with the emery cloth. From what I saw in the man. the seal doesn't look like such a big deal. If u can get it out with a pick or something w/o damaging it you can probably clean up the caliper well enough then put it back in. Smoothing the piston can't hurt either as, again, you will be replacing it. At least it will get u driving.

Author:	AdamIsAdam [ Fri Jun 23, 2006 11:22 pm ]
Post subject:
Well, I took the piston out and the boot is torn badly. There is rust and crud where the boot meets the cylinder. I guess this is the price I'm paying from the Pine Barrens and/or 52k miles mixed with various off roading trips. I'll buy a new caliper tomorrow, I guess.

Author:	Cacher123 [ Fri Jun 23, 2006 11:29 pm ]
Post subject:
All may not be lost! There is usually "rust & crud" around the outer edge of the caliper where the boot goes. As long as it doesn't extend down into the bore area it's usually ok. Try cleaning it up b4 buying a replacement. You may still be ok with a rebuild kit. It usually takes alot to waste a caliper body. Worth a shot.