Powerbandauto

To get straight to the point I replace the master cylinder, the pads, the rotors, brake shoes, the brake drums, and the wheel bearings. I made sure all the wheel cylinders and calipers were also good working order. Now I've cleaned out the proportional valve with brake cleaner got some gunk out of there and removed all hoses and lines for the front brakes and cleaned them out. My issue is I'm getting brake fluid to the rear and able to flush that but I cannot get any fluid to the front brakes to bleed them. The only thing I can think of is I bought a defective new master cylinder or is my proportional valve stuck? Anyone help me out. It is a 1983 Mazda RX7 GS with rear drums

chrisaleggett

1st thing came to my mind was bleeder valves fro those front calipers, might want to remove them and make sure they're not clogged with debris & air can pass through them. If that's not the issue maybe try bleeding it at the master cylinder or proportioning valve by cracking the lines. And work your way down to the calipers

Powerbandauto

That's what I thought too but they're not clogged either (very rust free car). When the plunger forces the master cylinder to move..

There's 3 ports on the master cylinder
the very front port allows fluid to pass (Rear drums)
Bottom port (Driver front) and side port (Passenger front) doesn't release any fluid? is that how they're designed or is that a faulty new part?

Both the old master cylinder and new one did the same thing if that clears anything up.

chrisaleggett

So if your not getting brake fluid directly out of the master cylinder, specifically at the mc port to beginning of front brake line then you need to bleed it out more before you deem the new/reman mc defective & especially if you said the old mc did the same thing.

Did you by any chance bench bleed the master before installing it?

craaaazzy

iTrader: (9)

Yep, make sure to do this.

t_g_farrell

iTrader: (1)

You need to stomp on the brakes really hard a couple of times. The proportioning valve is also
a fail safe and maybe not be letting pressure to the fronts like it should. I have had the reverse
happen where I couldn't get good pressure to the rear to bleed the brakes. It happens because
you had the lines cleared and the valve emptied out. So when I say stomp, I mean use a lot of
instance force on the pedal a couple of times. That usually unsticks the valve and allows
pressure to both systems.

BTW, I've never had to bench bleed any new masters when installed. Also the SA does have
bleed screw on the side of the master if you want to try it.