i have an 86 f150 i took it to get inspected and the rear brakes do not engage..i bled the brake system and installed a new master cylinderand nothing....i jacked the rear end up and place the truck in Drive while applying the brakes and the wheels roll .. Oh i also adjusted the rear brakes??

all replies greatly appreciated!!

 

Have you checked your proportioning valve? That is the splitter from front brakes to rear. If the shuttle valve in it has moved, it could shut off pressure to the rear and only allow front brakes to operate.

 

how do i check if valve is closed??? now it seems that the front brakes are locked up..im a change out the valve tomorrow..

 

well to check the proportioning valve its as simple as finding a paper clip and the valve. since your truck is an 86 i assume it still has drum brakes in the rear. on the proportioning valve take your paper clip and there may or may not be a small hole on the side nearest the front bumper if theres not remove the cap and use your paper clip to see if the valve moves. if it moves your gold, if not its no good.

 

I'd start at the rear wheels and work forward. Jack the truck on on jackstands. Open the bleeders and have someone press the pedal down. Does fluid come out? Yes:Problem is at that wheel. No work your way back to the proportioning valve. Do you find a fluid leak anywhere? Yes: Fix leak. No: Check proportioning valve. Has your brake fluid level in the master cylinder resevoir been dropping since you found this problem. Yes:Locate the fluid leak. No:Check slave cylinders and proportioning valve.

 

I have similar problem in Aerostar -87, https://www.fordforum.com/m_40881/tm.htm