Hi Folks,
I think this has come up several times but don't remember seeing any real explanation for it other than the bleed hole in the master cylinder being blocked.
It seems that not too many people are aware of the non-return valve in the early master cylinders (from about 1970 to 1978~79)?
I'm not sure but I think it's only fitted to the pivoting caliper type brakes to maintain a low line pressure and prevent return spring on caliper pivot pushing pads all the way back (because 'EVERYONE' adjusted brakes correctly to 0.006" at each service
)
Anyway, heres some pics, explanation at bottom
It fits into the end of the piston return spring inside the master cylinder.
If there is any corrosion dirt, goo, etc under it when fitted the small indent can't relieve pressure and brakes can drag.
How it works, the holes are on piston side of M/C, when pressure is applied the rubber 'flap valve' opens allowing pressure into line.
When lever is released the valve closes and most pressure bleeds off through the small indent (about 11.00 o'clock position, pic 2)
Added pic of 'complete' assembly, (left out circlip and washer which holds everything together and the wire circlip that holds dust boot)
PJ
