i bought an 1987 Chevy suburban 3/4t 4x4 with the tbi 350, and of course i knew i was getting a basket case before i bought it. Anyway, I'm having problems with my brakes on the truck. In the beginning i couldn't get the brakes to fully pump up like they should, so i ended up bypassing the rear height sensing proportioning valve an that didn't help the problem. Then i found out the master cylinder apparently was bad, so i bought a new one and bench bleed it before i put it on the truck in which it didn't solve the problem. Then i ended up replacing both front calipers, and changed the front brake proportioning valve oh probably 3 times. After i put the third valve on it, i got the brakes to pump up a little better than what they were previously. then about 2 or 3 weeks ago, i went an re-ran the rear brake line but still kept the height sensing valve bypassed but only bled the rear brakes. then i went an bleed the front brakes an now when I'm moving it around the house, the rear brakes lock up when i barely press on the brake pedal. at this point I'm getting fed up with dealing with the brakes on it, I'm still pointing fingers at the front proportioning valve as the culprit considering i got it from a junk yard. however, now I'm beginning to wounder if the problem lies with the fact that the height sensing valve isn't hooked up.
Can anyone tell me if that height sensing valve needs to be hooked up for my brakes to work correctly, or is there a way that i can "cheat" and get my brakes to work like they should without that valve? At this point, i found an aftermarket company that sells the front proportioning valve and I'm half tempted to order a new one in hopes it solves the problem. Any help would be appreciated