my mechanic took all the calipers off my car today so i could paint them while he fitted all the new discs and pads, no problems so far. put the first rear caliper on my bench at work and as i undone the bleed nipple it moved 1/2 a turn and then stoppedeven using all my bolt removing skills i couldnt get it out without up the threadso now my enginner has it to see if he can sort ot for me. what started as a simple job has now turned into a pain in the . whats more anoying is all the other 3 bleed nipples just came undone. could have been worse i suppose, it could of happened when he put the freshly painted calipers back on the car.