1978 f150,351M,4X4,SHORTBED,4SPEED. I have replaced everything I can think of,....Master,calipers,pads,wheel cylinders,shoes,hoses front and rear. I have not replaced the porport.valve or the Booster. These two items seem to be working right. Here's the deal..The truck will stop if you push on the pedal hard enough, but it seems to go all the way to the floor. No matter what,I cant get the brakes to even try to lock up. The other dat I was coming home from work and the brakes seemed to quit working. The pedal was very stiff, like I had no vacume to the booster. So, I pulled out the valve to the booster whil the truck was running to check if it was pluged up,seemed OK. I put my finger over the end of the valve to stop the leaking vacume and it kills the motor in 5 or 6 seconds. Is this typical to kill the motor by pluging off the hose to the booster? I have the hose routed to the back of the manifold right under the carb. Do you guys think I need a new MC and booster OR do I need to re- rout the booster hose?

 

It has been a long time, have you found out anything? I would suspect the MC or a bad bleed with the new fluid. In the bleed, did you bleed furthest wheel first and closest wheel last? Sounds basic but that it I just ran into when doing my brakes.

 

I still have not found the problem. I have a hunch that it is the newly rebuilt MC.

 

> I cant get the brakes to even try to lock up.

This is usually because the rear drums are not adjusted properly.

> The pedal was very stiff, like I had no vacume to the booster

Sounds like a bad booster, it does not need to be hissing to be bad.

In my experience, the best thing is to replace the mstr and booster as one unit.