Master Cykinder failure, take 2!

[RedSwinger]

Just had the second new Master Cylinder failure in 2 weeks. I converted the Dart's manual drum brakes to Power front disc brakes using a SSBC kit. The car was not pulling enough vacuum, so I had an electric vacuum pump installed. Brakes worked good for a few days, then the MC had a complete failure. Replaced the MC, and they worked fine again, for 2 days! Another MC Failure . . . Anyone have any idead? Thanks in advance for your help!

 

[66plyValiant]

to much vacuum ruining the rear seal in the master cylinder? It should have 18-22 inches of vacuum (usually rated at idle). But your test procedure should show the vacuum pump should have the same vacuum all the time I believe, no more than 22 in that case.

 

[slantsixdan]

to much vacuum ruining the rear seal in the master cylinder?

No.