So I have a 92 F-250 7.5 liter V8. As i was sitting in the turn lane at a light, all of the sudden my brake pedal sunk to the floor! Before when I was slowing down to turn into the turn lane, the brake pedal was nice and firm with good response, but like I said I was just sitting there and it just sunk. It still stops the truck, but freaks me out cause it feels like I have no brakes. I got home checked the brake fluid, and it was low, filled it up, and it did nothing. Any ideas why the brakes did that? and How I can fix them myself would be greatly appreciated!

 

It is either losing fluid somewhere or the master cylinder has failed internally.

 

you obviously lost some fluid somewhere, you have to find out where.

 

what DIY says. Check around all four wheels and brake pipes for any signs of fluid leaks. If none found then remove the two nuts holding the master cyl to the booster and pull the master cyl forward and look for any signs of fluid at the rear of it. If any found replace it.
It could also be something wrong with the rear brake shoes, you may have to pull the drums and have a look.
Could also be a bad RABS hydraulic control module, however check everything else first.

 

just had the same thing happen a month ago, it was a old leaky rear brake piston. put a new one in, and it helped

 

step on the brakes a few times, then get out and look for leaks on the ground. pay close attention to the inside of the 4wheels, and along the frame on the driver side.