hey yall i was bleeding the brakes in my 78 k5 and the back resivor ran low and apparently the proportioning valve kicked in and wont give pressure to my back brakes it has a button on the side of it but i cant figure out how to reset this so i can get pressure to my back brakes ive smaked it around to try and get the little ball inside loose im at a loss please help me out

 

those stupid things never move if you push on them, usually ive had them click free if you can get fluid moving through them. try bleeding the lines at the mastercylinder to make sure you got pressure coming out of there and all the air is out then at the out line on the prop valve if its not a rotted mess then go to your rear brakes. ive ran mine dry numerous times, mostly cause i build a truck or replace axles every other year and ive never rand into a problem.

 

how would you bleed the lines at the master cylinder?so my thing is if this dumb thing dont start workin again it says in the service manual(actually it mentions it but never tells you how to re-set it)its not repairable and i sure dont wanna change that thking out ..am i wrong or is that button supposed to solve this problem.if bleedin it at the master cylinder works and yall could tell me how that works ill definately try it .thanks yall

 

its kinda just like bleeding your brakes. have someone get in the truck and pump the pedal until theres a little bit of pressure on the brake pedal. if none ever builds up then like 10 times. have the brake pedal pumper hold the pedal down and someone crack open the lines one at a time at the master cylinder. so open one, when fluid stops coming out close it then open the other one and close it after fluid is done coming out. and repeat the process until no more air is coming out.

ive never really found a technique that matters if you do front first or back first i just kinda alternate

 

and that will open the valve and ill get fluid to the back brakes?cause it happend all of a sudden when that thing ran out of fluid bam all of a sudden i got no pressure on the brake pedal at all ..but the frnot brakes still bleed.

 

its possible... thats why i would start with bleeding out at the master first, if you get all the air out of the master then bleed at the prop valve and nothing comes out then you know its the prop valve.... but ive ran across issues like this with a few other cars and its usually due to massive amounts of air in the mastercylinder giving no pressure out to the rear lines. so hopefully that fixes your problem. i personally have never seen a prop valve go bad from running out of fluid. not saying it cant i just never seen it.

 

i bled the master cylinder and the outlines of the prop valve the light went off and now im gettin fluid outta the back brakes thanks man im pretty sure its fixed!

 

sweet. ive always been lucky with doing it that way. i dont know why the heck it does that but glad you got it fixed. and lucky you for not having rotted lines. i tried this on my 83 s10 years ago and broke 3 out of the 4 lines