Hello All. I have a '75 F150 that has power brakes. Disc up front and drum in rear. I restored the truck about 3 years ago and have just started driving it a bit. During the resto the brake system was "gone through" with a new master cylinder, calipers, pads, wheel cylinders, shoes, brake hoses, etc. The truck has good "pedal". Pedal travel is not far. Brakes do not feel spongy. However I just installed an automatic transmission and now I have less engine braking. I have found myself having to really chow down on the brakes to get it to stop. I almost rear ended someone last week. Therefore haven't been driving it much since this except to test the brakes.

The past couple days I have adjusted the rear shoes, checked the booster, and am running out of things to check. Everything seems okay, but obviously isn't. I had my dad test drive it to make sure it wasn't just me and he says that the brakes are definitely not right.

The first inch or so of the pedal does almost nothing. Then when you start to feel resistance you still have almost nothing. Then if you really jab them it will start slowing down. And sometimes the rear brakes will lock up. I found this out slowing down on an interstate off ramp. Not good.

I was leaning toward the booster. But I checked the booster and it holds vacuum. The brake pedal goes down if you start the engine with your foot on the brake. So everyone tells me the booster is fine. But I do not hear the "hiss" that power brakes usually give when you step on the pedal. The brakes feel almost similar to my dad's '74 F100 with manual brakes.

Any suggestions?

 

Do you have a vacuum reservoir ?

If not,Put one on and see if there is any dfference.

How about Booster push rod measurement to M/C ?

Is that correct ?

 

 

I checked some things this weekend. I cleaned the calipers where they slide on the spindle. I put some never-seize on them. While I had the front wheels off the ground I depressed the pedal just a hair and the front wheel stopped. Which makes me think the MC push rod is adjusted right. I will check the push-rod with a gauge one of these days just to make sure.

They are better with the adjustment and cleaning....but still seem to be a bit stubborn unless you really step on them. Then the rears lock up.

Maybe I have gotten used to my F250. It has the HD brakes. What a difference. But it seems that these should do better.

Is there any other test on a brake booster?

 

Whoops! Missed the Booster Test post somehow. Thanks!!

 

The way the ford brake system works is this.

The Rears come on First...then the main braking is supposed to be taken over by the fronts.

This means the rear shoes have to be adjusted correctly, the rear brake hardware is a not fatigued.

The BPPV must not be corroded inside from the truck sitting for an extended time. Rust is its enemy.

The caliper pistons must be able to slide with its chamber both directions easily.

Rubber brake hoses should not be swollen or crimped. (some mechanics use clamps to keep brake fluid from dripping during brake service)

 

You may have a bad proportioning valve

 

I agree, it sounds like a bad proportioning valve. These are not available from Ford anymore, but you could get a couple from a junkyard and try them, also a few companies do make them new as a replacement.

I was able to take mine apart and clean it thoroughly and it helped a lot. Instructions are available in a Chilton manual.