I posted this on the brake forum but no responses. So I thought I would try again here.

I just installed new rear brake shoes, wheel cylinders, hardware, & turned the drums. I have bled the brakes using a clear hose & a bottle to be sure I removed all air.
Now I notice that when I press the brake pedal it is hard at first then SOMETIMES it starts to feel soft and the pedal travels down a little. My thought was the master cylinder is bleeding by internally. The pedal never goes to the floor, and will stop the truck. If I just press on the pedal it is hard until I let up a little then press again.
Does anyone have any other thoughts on this or do you agree a new master cylinder is in order?
Craig

 

craig I think you nailed it. My 86 f-350 did the same thing I replaced all the stuff you mentioned on mine as well and had to replace the mater cylinder and that fixed mine. I also have a 86 f-150 and it did the same thing except the red brake light would come on on the dash when it would happen. replacing it fixed it as well. good luck scott.

 

Thanks, Scott.
That was my first thought just wanted to run it by others to see if there was anything I might be missing.
I'll order a new master cylinder, & install it.
Again Thanks Scott.
Craig

 

craig
i have an '86 f250 4x4 and i had brake troubles since i bought the truck in '05. i had replaced all that you've done, i also changed the brakebooster and master cylinder. i still dont have great brakes but they are much better.
james

 

I had a similar issue on my '83 f350, brakes would go soft and then I'd let the pedal up and they'd be fine again. As said above, it was the master cylinder. Autozone has them for $24 with lifetime warranty.

 

I concur, master cyliinder and brake booster should solve it.

My fix started just like yours, rear brake shoes, wheel cylinders (one was leaking), spring kit. That led to replacing the hard brake lines over the rear axle due to breakage during dis-assembly. Bled them out but when the truck was running, brakes still felt odd. I was running out of time and I needed something to drive (like "yesterday") so I handed it over to a local Ford Dealer Service dept (figuring it was either related to the master cylinder or low vacuum from a poor running I6 - carb was shot). Tn one day, they replaced the carb, master cylinder and power booster and now it runs and stops good (not great by new truck standards but as it is supposed to for an 82).

Good luck!

 

Here is the findings. I went & bought a new master cylinder, bench bled it. Ordered a new electric trailer brake controller.
So this afternoon I decided to install the new brake controller. The one I had was OLD STYLE & was the type that needed to be plumbed into the rear brake fluid line off the master cylinder. So I installed a new Reese's POD. Well when I got the old brake controller out I noticed that it had a very small leak internal. Well I installed the new POD controller, reconnected the rear brake line to the master cylinder bled it & it appears to of fixed my problem. Now I have a new master cylinder if I ever need one. I will drive it tomorrow to make sure everything is OK. If not I'll replace the master cylinder.
Thanks to all for your responses.

 

Ahhh, the trailer brake controller...Glad you got that figured out!