I am having a problum with my rear brakes not working I am thinking it may be the proportioning valve the pedal is very soft. Any Info?

 

Sounds like someone needs to do a complete flush of the brake system and possibly a change of hoses. Suck out all the fluid from the reservoir and clean it. Pour fresh fluid in it and crack open the bleeder valves in this order: Rear Right, Rear Left, Front Right and Front Left. Do this one valve at a time. Each valve will be open to gravity bleed till you see the fluid come clear then you shut off the valve and go top up the reservoir. If this doesn't work and you are sure you had no air bubbles in the fluid then you need to change your brake lines. I did that with a stainless steel braided hose and I lost an inch of brake travel.