The Stovebolt Site Forums The Parking Lot Big Bolts 46 2 ton brake question

Hey All

Im doing some shakedown runs in the old girl. yeah, finally on the road.
I had a brake question.
Note: its a 46 2 ton with power assist brakes.

question: when I drive it, after a few miles, the brake pedal get really hard, and in fact start to drag. What would cause this? a vacuum leak?
something with the check valve on the firewall?

Im confused, so advice welcome.

best regards

jay

of note, I installed a 261 with fenton intake and exhaust if that matters.

I couldn't find the previous thread on this same problem. Seems like some suggested master cylinder push rod travel adjustment and proper shoe adjustment were a couple of the suggestions. Try the forum search maybe you can spot that thread.

when i start up the truck, the pedal goes between a quarter and half way down when i brake. after a few miles its at the very top. he brakes actually drag at an intersection. no need to hold the brake.

Hi Jay,

Just an idea here. This happened to me in the past and it turned out to be a clogged relief hole (not sure of the actual term for that hole) in the master cylinder. It's very small and sometimes hard to see.

tony

thats a good suggestion, I will look tomorrow.

unfortunately, making sure the vent hole was unplugged didnt help the situation.
even with the master cylinder cap unscrewed, the pedal is still rock hard.
sitting overnight it softens up, and takes a few miles to get really hard.
on the way back from the hardware store today the brakes seemed to be dragging. I was at an intersection with a slight incline and the truck stood still.

Hy Jay_Brown, it sounds to me like the master cylinder plunger is not uncovering the compensating port when it returns to the at rest position. Check to make sure there is clearance between the pedal linkage and the master cylinder plunger, hope that helps.

thanks 3b, I will open up the gap tomorrow and see what happens.