my 56 f100 with a volare front and a nine in rear all new seals brakes , has a issue of a heating prob lem if driven over 5 miles r so the brakes are expanding and i have to pull over n let em cool , both front and rear , yes i was using a inline residual check valve in the front and rear , took out the front one and they were doing well ,now the rears are doing it as far as i can tell , from the smoke coming off, from my 12 mile drive today , exhaust is around 6 inches away from master but diaphram under floor is only about 2 inches away didnt think that would do it though, and i have a plate between the booster and the exhaust ,, any help or ideas appreciated oh i also have a wilwood adjustable proportioning valve inline ,,
Do you have free play between the master and the pedal? If not that's your problem. Are all the rubber hoses new, including the one from the frame to the rear end?
Simplest thing to do is shorten the rod from the pedal into the back of the master. Go about 1/8" of an inch (or so many turns) and see what happens. But keep track of what you do in case it needs to be un-done.
I had this very thing happen when I put power disc brakes on my 66 Suburban, only got a couple of miles from home on the first test drive, had to sit and cool off before returning home. Pretty common problem when using a mix of components.
Ok thanks ill check the freeplay ,i had more but adjusted the proportioning valve today for more pressure ,could that have done it? Sent from my LG-UK495 using H.A.M.B. mobile app
If you find the free play in the pedal to booster push rod is OK; could check the clearance between the booster push pin and the master, easy way to check if too tight is to loosen the nuts that retain the master and slip a couple body shims between the master and booster. Pretty common with mixed or aftermarket parts.
Whatever you try, do 1 thing at a time so you know what worked. Adjust 3 things and if it doesn't work, you just compounded the problem.
The booster push rod should be connected directly to the pedal, and any free play is by design within the booster control valve. The pedal has to be able to return farther, when disconnected from the booster, to make sure the booster can fully return. The pedal should have it's own return spring and not rely on the booster. The booster output push rod should have about .040"-.060" clearance with the master cylinder primary piston, and this is checked with full vacuum (about 20"Hg) applied to the booster. I always start out with the adjustable proportioning valve set to max rear pressure and adjust down if necessary. As for residuals, no more than 2 lbs to discs only when the master is below the floor, and 10 lb external (or stock internal) to any drums, regardless of master location.
A couple of things come to mind. One is that your fronts are floaters, sometimes that don't slide well and drag too much after being set. Lithium graphite in the brake pins will help that or a good polishing if they are old pins. That said you say its all 4 we just went through that with @Tim 's '46. He changed from under the floor to firewall, and failed to out a return spring on the peddle. It was my bad because I didn't notice it and should have right off. The weight of the peddle made just enough pressure to drag the brakes without keeping him from driving it. The result hot brakes.
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