my 2 cents..
i guess the brake is been hidden behind that cover for ages,
therefore its probably never been checked cleaned or ....till it shuts you down.
i should take the caliper apart ,the piston out ,clean it good
check the rubber rings for shape ,hard area,s or wear.
the piston when cleaned must slide nicely up and down in its cylinder
then assemble it again and bleed it thoroughly,
when your busy ,put in new brakefluid too
oooww btw ..is your lever not adjusted too tight
had it once with my rearbrake ....tooo tight adjusted and its continuing making contact with disk,
due to building up pressure and then heat at the caliper
good luck then
freak