I've heard alot of people talk about diagnosing a MC failure, but how can one really tell if it is bypassing. It got me to thinking about how they really work.

There are two cylinders, primary and secondary, in line with one another. The primary goes to the front brakes, and the secondary to the rear brakes. What puzzles me is the relationship between the fluid in the reservoir and the fluid in the cylinder. How does the fluid get sucked into the cylinder and stay there. If I push in on the caliper pistons the fluid is pushed back into the master, right? There must be a little port that is only available when the pistons are completely static (brake pedal not pressed) to allow fluid into and out of the actual cylinder from the reservior?

When I press the pedal down, my fluid level rises in the reservoir. Is this correct? Seems that the level shoud remain constant unless you are expanding brand new calipers, etc. If it's going up then the MC is leaking back into the reservoir, right? If my MC is working fine, then will the fluid level just remain constant when the pedal is pressed?

BJ

 

You got it right. There are two relief ports that get sealed up when you press on the brake. They may squirt just a bit as they get closed up.

 

So the level should not rise when pressing the brake? Crap, so it looks like the brand new master cylinder is bad. This one is from autozone, which I've never had problems with before but suddenly have gotten a bad wiper motor and now a bad master cylinder. Don't they test these things? I hear people rag on autzone but until recently I've had no problems. I guess I'll have to swap in another one in the morning. I don't want to chance getting another bugus one...anyone know of a reputable place to get one? Really getting tired of working with brake fluid.

Bryan