New Master Cylinder Leak

[Baron3-6]

Back to the forums after a while! I recently replaced the master cylinder on my '52 M-37 with a new made, identical to GI part. I had some difficulty getting the old "post" (see picture) removed from the pedal....so I simply left the old post in place, its adjustment looked the same as the new post....installed the new MC, bled the brakes and wala...off and rolling fine. Came back after storing her for a month and the MC resevoir is dry and the MC is leaking from what appears to be around the boot. The original vent line was cut and crimped so I replaced it with a stub of open line as a vent for the MC (I was under the assumption that air flow was needed for the MC to work correctly).

What are some opinions on whats going on here ? Is the post adjustment off and now ruined the MC? Does the vent line need to be sealed off? Thanks guys!

 

[majorhitt]

The boot's function is to prevent foreign matter from getting into the brake cylinder area and causing damage to the cylinder wall. This said Your cylinder wall may be scratched and it's leaking past the piston into the boot area.

 

[Baron3-6]

I thought it might be the cylidner, but it's a brand new part......unless the 6-8 hours of driving I've done ruined it.... could improper shaft adjustment lead to cylinder failure? The old shaft I left connected was adjusted the same as the new one.

 

[3dAngus]

I replaced mine a few months ago. It sounds to me like the master cylinder was a rebuild rather then new and it didn't go well. I would just replace the M/C again and try it again.

But yes, I did seal off the vent line. You don't need it once the full system is properly bled off.