I am having trouble with my rear brakes. They are weak and are not locking up on dirt roads like they should. the pedal feels stiff (not soft) but I had it on jack stands and had an assistant apply the brakes and I could fairly easily rotate the back wheel while the front were tight. Ive bled the brakes over and over and it hasn't helped. There is no fluid loss or leaking anywhere.
put new rotors and pads and greased the slides which it needed
I took the proportion valve off and cleaned and blew it out. didn't help.
Of course I think (as I did before) that it is the master cylinder and ordered a new one (looks like people have trouble with remans).
Here's the thing . . don't they usually slowly sink when steady pressure is applied if they are bad? That is not the case with mine. I would seam that with two reservoirs, that may not be they way the feel if only in piston is bad. Any advice is welcome.

 

Guessing the dual brake system applies pressure to a one front and the opposite rear brake. Not one system to the front and one to the back as might assumed.

How much brake fluid flow are you getting out of the rears when bleeding?

When applying the brakes, can you see the rear brake piston move?

Are both rear brakes acting the same way?

 

Looks like the system some how mainly divides between the front and rear but there is a proportioning valve that seem to somehow redirect some of the pressure between the two. The valve has 6 ports and I could not make any sense of it.
I am getting a decent amount of fluid but it is slow to come. Like its restricted. Both the with the mighty vac and an assistant pumping. My new theory is that maybe I lost fluid in the rear chamber at some point and it needs to be bench bled. But then would I get any fluid at all if that was the case?

Both rear brakes are acting the same.

I cant see the rear pistons move (havent looked) but it it does apply some braking just not enough.

 

Does the car have ABS?

 

No ABS. I guess in 93 it was and option. Should have mentioned that.

 

Got the new MC today and have tomorrow off so on it will go!!

 

The link below has info on the proportioning valve (dual proportioning type).

http://www.autoshop101.com/forms/brake08.pdf