Just went through the brakes on my 1979 F-250 2WD 4.9L I6. New Master Cylinder and Brake Booster, new front calipers and pads, new flex hoses that attach to the calipers, and had a successful brake bleed to all wheels (old fluid and air bubbles pushed out). When test driving the truck stops well and the front wheels even lock up when pressed hard, but i can't help but notice the booster isn't helping much or as much as it should. Pedal seems tough. Any ideas? Probably going to check vacuum leaks in the morning, but does anyone have any other advice or tips? Any adjustments that I may not know about?

 

Other than make sure the booster is getting vacuum not much else.
Why did you change them out? Was the old booster & master leaking?
Dave ----

 

Did you adjust your rear shoes?

 

The brakes haven't been touched in probably 15-20 years because it had been sitting in an open shed for that long. My dad wanted to change out everything just to be sure.

 

Ok I can see doing that so you don't know if they worked before or not then.

May also want test how much vacuum the motor is pulling.
If it is only pulling say 5 hg it may not be enough to work the booster.

Also I would replace the booster hose if you have not yet.
The hose can look good on the out side but falling apart on the inside and being blocked.
Dave ----

 

We didn't do anything with the rear brakes except bleed them. Don't want to take those apart if we dont have to. It's a Dana 60 LSD so getting the drum off means pulling out the axle shafts which isn't fun. We will if we have to.

 

Thanks for the tips! I'll let yall know when I figure it out.

 

Do you notice the brakes being any better with the motor running or not?
Did you replace the seal between the booster and the master cylinder?

 

Look at the check valve on the booster as well , might not be working if you reused the old one

 

there is a seal that goes in the front of the booster right behind the master cylinder. if you don't have that in there it will cause the symptoms you're talking about.

Sometimes it's inset, sometimes it just pops in . sometimes it's like a boot. in any case it has to be there.

 

Did the rear wheel cylinders have a good, pressurized stream of fluid, or just ooze out? If not a good stream, the wheel cylinders could be sticking/stuck, or the flex hose between the main line and axle collapsed.

I bought a car that had been sitting for 12 years, and the brakes acted like yours. Found the flex line between the rear axle and main steel line was totally blocked. Replaced line and it would stand you on your head.