Datsun Roadster Forum-311s.org

The piston returns by a spring a lite spring it can jam and not return pushing fluid to the back chamber , the front seal flexes more ...in other words if it leaks into the rear instead of pressurizes the lines its held by the that cant expand or contract .that explains it being low , no leak , then sealing
a on car lines off bench 2 man bleed will tell you everything in 6-10 pumps ....is it driving now or still a static thing ?

Mine leaks prior to the bubble seal apparently between the inside breaker and the firewall itself. New master cylinder. Is there a gasket between the inside bracket and the firewall??

I meant the leak seems to occur on the inside of the firewall between the firewall itself and the inside bracket that holds the cylinder mount. The bubble gasket seems ok. I don’t think this makes sense unless the cylinder itself is leaking

Now that I’ve taken out the master cylinder, I see there is no way to leak unless the rubber bubble gasket is crimped or bad.

Now that I’ve taken out the master cylinder, I see there is no way to leak unless the rubber bubble gasket is crimped or bad.
I’ve got in on my bench, air bled out and now it’s not leaking!! What the heck? Any ideas out there??

Yeah that's how /where they leak
If the cup seal to cyl leaks it leak out the back using dot3 fluid ?

Yup cat 3. I talked to SinCity and he sent me a new one immediately. I haven’t installed it yet but he said they rarely fail like this