Hello,

I have a 1978 F250 2wd with a 6.6L 400.

Yesterday i was driving around town and suddenly my brake pedal went all the way to the floor and lost almost all pressure. I have almost no brakes, but i am able to stop the truck if i push the pedal down extremely hard. The pedal will come all the way out, but goes all the way down to the floor when i press it in with no resistance.

I was having a lot of brake problems so recently I:

Rebuilt the drums with new shoes, springs, cylinder
Replaced the Pads on the calipers
Bleed the brakes

They work working fine, but now this happened and i'm not sure what would cause it.

Before, when i pressed the brake pedal real hard i could feel the booster catching and it feels like the booster was slowing down the engine. Now, if i press down the brake extremely hard it doesn't feel like it's catching. I pulled the booster check valve off and it IS getting vacuum.

Does this sound like a bad brake booster or Master cylinder? Let me know your guys input!



Thanks.

 

Also, I checked the fluid level and it has stayed the same, But the fluid has turned Brown.

 

Have you looked under it for signs of a blown line or cyl?

 

Sounds like the master cylinder is leaking internally.

 

Masters bad if it goes to the floor with no resistance.... brake booster would make it extremely hard to push the pedal it would not want to go to the floor.

 

Thanks a lot for the Info. Im going to replace the master cylinder tomorrow. Hopefully that fixes it!