Seized piston.

[StumpyFingers]

Just been into the workshop to service my brake calipers, as one kept binding.
Got it off and removed one piston, the other was solid, it took three and a half hours with penetrating lube and mole grips to get the thing out of the caliper.
Checked the recess where the seals sit and got enough grime out of them to fill a thimble cleaned them up and fitted new seals, the new piston went straight in with no problem.
Got the next caliper off and flew through the replacement of the pistons and seals.
Started to bleed the brakes and one started to leak so went to tighten the bolt and the banjo bolt sheared its head.
Got the reminder of the bolt out with a screwdriver, then had to get home to search my tool box for the spares I knew I had.
Bringing the bike home after I had fixed the calipers it felt like a totally different machine.

[Mervinh]

you are lucky penetrating oil and grips got it out. i have had to hook a grease gun to old RD ones to hydraulic em out in the past, sometimes an airline,(I use one off the lorry air system) will shift em but be careful cos they come out mighty fast and will damage things in the way
Merv

[ChrisH]

i have had to hook a grease gun to old RD ones to hydraulic em out in the past,

Had to do the same thing when I overhauled the TA front brakes recently - works a treat when the air line won't shift the pistons. Like you say Stumpfingers it certainly makes a big difference esp. as I fitted braided hoses at the same time