Rear master cylinder

[qual996]

Just returned from a run out and have totally lost rear brake.
The pedal just drops completely down, isn't there an internal spring that would always return the pedal to the 'normal' start position?
The reservoir is full but no fluid exudes from the calliper nipples and with the floppy pedal I cannot pressurise the system.
Suggestions please where to go first, I'm wondering if there is a blockage between the reservoir and the master cylinder, anyone had similar problems?
thanks for any advice
John

[George 350]

Hi,
Sounds like the master cylinder piston has stuck/siezed in the pushed in position. If it has, the only thing you should do is strip the master cylinder down, remove whatever is causing the sticking (usually corrosion) and reassemble with new seals and some rubber grease.
You might be lucky and able to free off the piston by either pushing the pads back, or you will have to remove the hydraulic hose and push the piston back with compressed air. As a last resort, you could use a pin punch but be gentle with it if you do.

George.

[qual996]

Thanks George, I thought that might be the first port of call, as ever I was hoping for something less demanding! Lazy me.
I'm not home till Thursday so next weekend should throw some light on it,
Ta
John

[qual996]

Hi George
You were spot on, it was the master that was stuck which seemed to have occurred as a result of a blockage between the resevoir and master and then 'drying' out although no evidence of leakage.
All released, cleaned throughout, still some small crap being exhausted through the caliper nipples but at least we have a brake again.
Thanks
John