Hey all, got a ‘77 f250, 400 engine, 2wd, front disks and rear drums, manual transmission, vacuum brake booster. I noticed my brake pedal was pretty spongy with the engine running but firm with the engine off. I know the vacuum booster has something to do with that but I feel like it’s too soft, and takes a while to stop, and the pedal almost goes completely to the floor, especially compared to my daily driver. It’s starting to feel a bit sketchy. My first thought was to bleed the brakes. Started at the rear passenger side, it was very hard to bleed the brakes, the pedal was very stiff and barely any fluid was coming out. Same goes for the driver side rear. After (I thought) all the air was out, I moved to the front, and they were super easy to bleed just like any other car. Anyways bleeding the brakes didn’t change a thing, at least I got brand new fluid now. I genuinely have no idea what this issue could be. Bad proportioner valve? Drum brakes not adjusted? Bad master cylinder or brake booster? No brake fluid leaks from what I can see, unless my wheel cylinders are leaking and all the dust in the drums is soaking up the fluid. When I get the chance I’ll take the drums off and have a look. If anyone has any ideas in the meantime it would be greatly appreciated?

 

Just a minute here ...

You simply bled the rear drums without pulling them and inspecting?

It sounds like the rear cylinders are frozen.

Proper rear drum shoe adjustment also determines correct pedal height on a DISC/DRUM setup.

 

Yeah I currently don’t have access to a jack and stands, I don’t drive the truck often so I figured I’d bleed the brakes first just to see if that’ll do anything. Looks like I’m doing a brake job soon