Swapped out drum for disc brakes while going to 3.73 rearend. In the swap changed out the propotioning valve and master cylinder. Bled the brakes from front to rear. Did not change brake lines since everything fits. Can not seem to get the back brakes to grab and was wondering if anyone has any ideas? Thanks.

 

Did you bench bleed the master cylinder?

If not, then it's full of air that you'll never, ever be able to get out by bleeding it on the car, no matter how many gallons of brake fluid you run through it; because the lines aren't attached at the highest point of the cylinders. A significant pocket of air will remain trapped in the highest point, forever; and the pedal will remain mushy.

Start there.

If you put on the old-style cast-iron disc rears, that would help explain it too; those never work right, until you modify the proportioning valve and install the caliper recall kit to the calipers. They'll never work really very well, but with all that, they at least work as well as the drums did.

 

Another thing that may help is to bleed the brakes starting with the wheel farthest from the master and working towards it.

RR,LR,RF,LF

 

My brakes suck too. Can you tell me specifically what I need to do to the prop. vavle and what kit/where can i find it, for the calipers?

88-Iroc
4 wheel disk
new master cylinder
new vacuum assist
100% new front brakes
newer pads on rear
1 newer rear caliper
TOTALLY bled system
Bench-bled master cylinder first

Any other ideas?

 

I have the same problem and have replaced everything but the proportioning valve. My brothers 92 RS with drums brakes 10x better than my iroc!

What do i need to do to modify the prop. valve?

What recall kit are you talking about?

Please help!
thanks.