Question on brake master cylinder

Have had some trouble bleeding the brakes on the '32 we are working on.

Decided to take off the master cylinder to check it. It is an 1 1/8 bore, probably a rebuilt Corvette type master cylinder.

We plugged both front and rear ports, and the master cylinder piston is hard like it should be. However, if we crack either of the ports, the is no pressure on the master cylinder piston.

How can this be, as the cylinder should maintain pressure for a failsafe operation, should one brake cylinder let go?

 

uh....you don't quite understand how they work. When one side of the brake system goes out, the piston for that side will bottom out...then the other side will work.

So it's important that you get full travel of the master cylinder (dry), before the pedal bottoms out on the floor! most guys don't realize this, so most dual master cylinder upgrades won't actually work as a failsafe, might as well have a single in it.

A dual cylinder has more travel than a single.

 

Learn something new every day, thanks squirrel!

 

Quick way to check if you have sufficient travel with a dual cylinder is to open a bleeder, and see if you still have brakes.