Hey guys, my brakes are hissing from the inside of the cab. They are holding pressure and perform fine. The air leak is coming from where the rod passess thru the floor. Its not losing presure like you would expect if the master solenoid is shot but maybe something is up with a seal in there or something. The intensity of the hiss is variable as I mash the brakes and occasionally completely stops in some positions (especiall if I hook my foot around the pedal and pull it back) Not too sure what the large donut looking piece is called in the engine compartment (booster I think) but is this something thats going to be costly to fix or can I just tear it out and replace some seals?
Any suggestions?
THanks, Jon
1986

 

Sounds Like The Power Brake Booster Leaking Vacum.

 

Yeah I figured that was the problem but do you have any idea on how to fix it? Does the entire unit have to be replaced or just some seals???

 

The break booster is leaking and you can use a booster from 80 to 96 f150. the push rod might be offset a bit on a newer one but it worked fine for me. Dont be afraid to use a used booster, it's a rare problem.
Ron

 

I Agree