I have a 1995 f250. A couple weeks ago, I did a brake job, all four corners of the truck. Brakes worked great, drove it for a couple days and parked it and went on vacation for a week. When I come home and hop in the truck, the brake pedal falls to the floor. My first thought- master cylinder. Then I turn key, and the red brake light was on, along with my amber abs liight. I check the cylinder and its almost empty, but I topped it off while doing the brakes. Also, when I pump the pedal with the engine off, it doesn't build pressure like the booster has a leak. So I don't know what to condemn. Input is appreciated!

 

It's gotta be leaking somewhere, have you looked all over? Even inside the stupid drums? Sometimes the fluid leaks out and trickles along the frame or whatever and ends up where you wouldn't expect it.

I'd say since it ran out of stop juice, you got air in the lines now. Refill it, check for leaks everywhere, and fix as needed.

 

I checked over all the lines and fittings and couldn't find any leak, but I never pulled the drum off. I'm confused why the brake booster wont build pressure though?

 

Honestly I would think if the reservoir was empty, you would see it leaking out of the drums. But it can't hurt to check, stranger things have happened.

The booster won't build pressure as in it won't provide any boost any you have a hard pedal?

Or the pedal goes all the way to the floor as you said in your previous post?

 

You have a leak. Brake fluid doesn't evaporate, so it had to have gone somewhere. The master cylinder could be leaking into the brake booster, the wheel cylinders could be leaking into the drums, a steel line could have rotted out, etc. Fill the reservoir and have a helper watch under the truck as you pump the pedal (engine off). If its a line you'll see it begin to spray and drip.

The reason for the soft pedal is you now have air in the system. Air is compressible, fluid is not. The booster only works when the engine is running and supplying vacuum.