I need some brake help please

[nychevyman]

I have a 67 stepside that i have been driving for a few years.
4 wheel drum brakes. worked great no issues.
the pedal went to the floor and stayed there at a stoplight.
I could not pull it up and the spring is fine. i gassed it away from the light and I felt the brakes release and the pedal came up.
with it in my driveway it will sink to the floor, pushing it in just half way it will suck itself down.
if i shut the truck off it will release and come back up in 10 seconds or so.
its a short height, fat booster 8 3/4" around approx
i have 20" of vaccum in the line from the intake
the check valve is good.

[hamjet]

Sounds like a faulty booster. when you accelerated hard the vacuum went to zero, releasing the brakes just like it did when you shut the truck off.. 2 cents..

[slikside]

Originally Posted by nychevyman

I have a 67 stepside that i have been driving for a few years.
4 wheel drum brakes. worked great no issues.
the pedal went to the floor and stayed there at a stoplight.
I could not pull it up and the spring is fine. i gassed it away from the light and I felt the brakes release and the pedal came up.
with it in my driveway it will sink to the floor, pushing it in just half way it will suck itself down.
if i shut the truck off it will release and come back up in 10 seconds or so.
its a short height, fat booster 8 3/4" around approx
i have 20" of vaccum in the line from the intake
the check valve is good.

This sounds like a Master Cylinder issue to me.

And you can check your vacuum booster like this:

1. With the truck not running, press and hold the brake pedal.

2. Start the truck.

If the pedal moves closer to the floor when truck starts...the booster is good.

If pedal doesn't move, it's bad.

Hope this helps.

[57larry]

have you thought about going with disc bakes? maybe now's a good time

[nychevyman]

i dont mind the drums they stop great when i'm not having this problem
I have done some reading and it appears i need another booster and to drill a link hole that is 1 1/2" lower than the one in the truck. my pedal is high

[jdalexa84]

I agree about the brake booster sounds like it is faulty. I would try to get it stuck down and with the truck still running remove the vacuum from the booster and see if the pedal comes back

[tdangle]

I agree with slikside. I think you need a new master cylinder. I have had boosters fail before and it just makes it very hard to stop. More pedal pressure needed than non-power brakes. I think the piston is sticking in the cylinder. Just had this problem with mine. Sitting for 10 years was just too much. On my truck the front brakes locked up and wouldn't release. Loosened the fitting for the front brakes at the MC and brakes released. After rebuilding the MC, brakes work much smoother.