Front brakes sticking

Had the master cylinder rebuilt with new OEM parts... by a reputable shop..it occasionally stick...if I crack the bleeder it releases....any ideas what it could be? Howd u fix it?tia

 

Both sides stick

 

did you rebuild the calipers?

 

I agree with XJ550H. Probably calipers and or brake lines.

 

No I haven't... I was searching the forum and some guy described same problem.. said calipers were gummed up inside a channel

 

could be the pressure relief hole in the MC. there's 2 holes in the bottom of the reservoir, a big one and a small one, if the small one gets clogged the pressure stays on the caliper.
take the cap off the MC and quickly squeeze the lever, you should notice a little shot of fluid come out of the small hole. be careful sometimes it squirts out, cover your tank with plastic bag and keep your eyes out of the way

 

If you only rebuilt the master cylinder, prepare to have endless problems with the brake system until you rebuild the rest of it (emphasis on YOU. Quit paying shops to do the easy work).

 

OK maybe I'm crazy but a I see a float with a c ring on it I removed it.. what small hole and big hole r u referring to?

 

The float is for the brake fluid level warning. Which XJ750?
On the Maxim the two holes are visible at the bottom of the master cylinder reservoir; on the Seca you have to disassemble the master cylinder to make sure the holes are clear.

 

Seca...I'm assuming I'll have to rebuild calipers then...I'm not gonna open them without rebuilding them

 

Evan / Brakes "sticking" wont release, is a common problem with all XJs The brake calipers need to be "rebuilt" cleaned with new seals installed. The seals harden over time and will not allow the piston to retract. This is not a hard job if your new to this. Now is a good time to do all 3 calipers. Order the correct K & L kits, 2 for the front 1 for the rear. The rear is a different kit and part#. Each kit contains 2 seals that fit a groove inside the caliper bore. The rear may have a "bellows" type outer dust seal. First start with the Front Right side caliper, this is the easiest to do for practice. You will need a 4" C-clamp, a small funnel, 2-bottles of brake fluid, brake cleaner, a small brass brush, an old tooth brush, and some steel-wool. No other special tools required. Cover your tank to protect it from brake fluid. Remove master-cylinder cover plate, so you can add fluid to reservoir. Remove caliper mounting bolts, do not remove brake line at this time, lay caliper on flat surface, "milk-crate" remove brake pads, place caliper in a small pan. To remove the piston from the caliper, squeeze brake lever, this will pump the piston out of the caliper bore, add fluid as needed to master-cylinder reservoir, the piston may cock a little toward the end, straighten it out, and continue pumping, till piston drops out of the bore. Remove brake line from the caliper, NOTE- there are 2 copper crush washers on each side of hose fitting, dont loose em, make sure you put them back on. Take caliper to a clean work surface, clean and polish piston. remove the 2 rubber seals from the caliper bore, use a small screwdriver. Clean grooves with small brass brass brush and brake cleaner, clean cylinder bore with a soft toothbrush and brake cleaner, remove bleeder fitting, spray brake cleaner through each hole in caliper body, if you have compressed air use it. Next coat inside of caliper bore with clean brake fluid, install the new seals, just push them back into grooves, coat the seals and piston with brake fluid. Drop the piston into the caliper bore, ensure it is CENTERED, using your thumb, press down on piston, you will feel it "click" as it goes past the 1st seal, rotate the piston around, you will feel when it is centered on next seal, again push down on piston, you will feel it "click" as it goes into 2nd seal. Now using a C-clamp-Mount it to a vise if you have one, and use a small piece of wood to protect your caliper, slowly press the piston past the 2nd seal, and All the Way into the bore, this doesnt require very much pressure, if you are forcing this step, STOP the piston is not centered on the 2nd seal, and will tear the seal. Next stand caliper upright, replace bleeder fitting-leave it open, fill caliper with brake fluid till it runs out bleeder fitting, then close it finger tight. Re-attach brake line to the caliper, Ensure you have installed the copper crush washers on each side of fitting. Place C-Clamp back on caliper to hold the piston fully depressed into bore, this makes bleeding a lot easier-quicker. Next fill master-cylinder reservoir with fluid and open bleeder fitting, the front right caliper will almost gravity bleed its-self, bleed caliper until good tight lever is felt, remove C-Clamp, install brake pads, mount caliper back onto bike, again depress brake lever and refill reservoir until good tight lever is felt. Before replacing reservoir cap, pull off rubber gasket, and clean under-side of gasket and cap, this is usually full of crud, that you dont want getting back into reservoir. Ok O.J.T. complete, not so hard, also when "rebuilding" calipers clean and inspect all sliding surfaces and pins. Next do Front Left Caliper as before. Re-install and bleed it till you get "Some" pedal back. Ensure you refill Rear master-cylinder with fluid about every 2-3 times you open the bleeder fitting. Now for the rear caliper, remove caliper and pads as before. There is usually a split ring that holds on the "dust boot outer seal" lift up the split ring and remove the dust boot seal. A tab holds the split ring, spread the ring and remove it from behind the tab holding it.Pump the piston out of bore, clean and install new seals, reattach brake line, with C-Clamp in place, bleed 2-3 times only- until you have fluid, Then move to Front Left Caliper and "Stay on it Only", and continue to bleed until you have a good firm pedal. Then re-install rear pads and caliper. Refill reservoir, clean all disks and brake fluid from bleeding. Now go have fun riding an XJ with-out brake lock-up problems.
Good Luck / LtDan