Mechanics

GMC TRUCK BRAKES PROBLEM

1976 GMC Truck

76 gmc k1500, have replaced calipers, drums, master cyl & factory perportioning valve. Have no front brakes & rears lock up. After repeated checks it appears the perportioning valve is not centered? Is there a way to reset it? Other ideas? Could the lines in be swapped &
Avatar
Gadman
October 17, 2012.



Did you bleed the brakes? The pin on the proportioning vavle should be held open during bleeding.

JDL
Oct 17, 2012.
Yes, how do you hold the pin open? Have never heard of that before & can it be reset at this point?

Tiny
Gadman
Oct 17, 2012.
You can have a helper hold it open. There is a tool for that, use to be a tool. I believe in the past, I have used a small vice-grip to hold the pin. It's been a while since I worked on that model year.

JDL
Oct 17, 2012.
Is the pin in the center of the brass plug on the lft side? There is not enough to get ahold of. If I were to loosen the plug & pull it will it center the valve? They have been bled several times & all lines are fresh fluid & no apparent air in system, just no pressure to the fronts. Does the valve need pwr? I dont care about the light, hasnt worked in years.

Tiny
Gadman
Oct 17, 2012.
It's been a while, I'd have to look at it. That little pin, you either push it in or pull it out. I can't remember? I tried looking up that valve on an inline partsbook, couldn't find it. I thought maybe looking at the valve would jog my memory.

JDL
Oct 17, 2012.