Can a proportioning valve cause brakes to hang? We have been completing a 79 f-150 that was a mud truck and was an engine swap that was started by somebody else. The rotors, drums, calipers, wheel cylinders, booster, master, friction material, and most lines have been replaced. All of the remaining components have been cleaned and lubed. For some reason, we at times have a noticeable brake drag. I can feel it both in driving (it is a manual transmission, so at stops, etc) and at the individual corners when jacked. Am I missing any other potential causes? Any input is appreciated.

Thanks!

 

I don't think a PV valve will cause drag.. it doesn't apply pressure.

It sounds to me that either the booster has an internal vacuum leak or the brake pedal push rod is not or was not properly adjusted.

 

As HIO said, it's more than likely the brake pedal push rod isn't adjusted properly. I just battled this myself a few weeks ago and that's what it turned out to be.

Mine was run out from the end of the adjuster almost 3/4ths an inch. It needs to be somewhere around 3/16ths or so. Too much will cause all four brakes to drag like there is air in the lines, and will make an otherwise healthy truck feel like a dog.

Hope you get it figured, let us know if you need anything else!