tkoppab1

Whats up everyone, I've been having an issue that I cant seem to solve or find doing research for days now.

I have a 67 dual resevoir master cylinder on my 66. I have new rebuilt calipers up front with new lines, new rear brakes and cylinders on the back and a master i replaced like 2 yrs ago. So here's my issue, the smaller reservoir which from my understanding is for the rear brakes always goes empty on me. Thankfully I have the dual so the fronts work fine but the brakes are still kinda crappy.

Ive read that the rubber gasket on the master sometimes causes leaks because it soaks up the fluid but I highly doubt it will soak it up that quick. The area around the master is wet but I find myself always filling that small resevoir and I dont always avoid a spill. I know I have to clean up the area and find out exactly where it leaks from but here is my question.

Have any of you had this situation where only the small resevoir leaks? I mean ive bled the system and checked all the lines at the tires and they are good. Id appreciate any help. thanks!

67mustang302

The front and rear of the cyl are isolated through seals, so you can have a seal for 1 bowl of the m/c leak. Check the entire line to the rear brakes for leaks too. You definitely have a leak somewhere.

bop11

Have you pulled the rear drums and looked at the cylinders?

barnett468

yes, pull the rubber boot back on the wheel cylinders if there are no obvious leaks. seal the master lid. it should not leak. then look for leaks there too.