bad brake fault on rrc 1992......any ideas?

hello all, being as i have lots of range classics about, i am landed with a fault I cant fix.
the brake resevoir became porous, and having fitted one now, I have a problem where the front o/s brake locks up and stays locked up. I cant seem to stop it from happening whenever I try to run it.
ANY help on this would be greatly appreciated, and I hope to add a bit of help to you all in the future. I have been running rr classics for a long time and 2 of us do up to 2000 miles a week each, so we get allsorts of niggles.
cheers
bernie

take yer caliper orf and push the piston out as far as yer can without exposing the seal. then wack some coppaslip on the side of the piston and bung it back in

lovely, will try..........
The car was ok until i changed the main unit, coincidence?
cheers.
p.s like the give a ***ometer

HI if the last post dont fix it try new flexible hoses to the caliper, i have known them to collapse inside and act as a one way valve, allowing fluid to pass through but not return.
Good luck.
Sprox

I'd never had one do this before, so i'm chuffed the problem sounds tangible, fair play

just check yer piston furst before you break into the system.. saves on all that bleeding and stuff

I'll get onto it and get back to you, nice one