07 F150 Brake Pedal Travel
 

Hi guys. I'm new around here. Tried searching existing posts for my problem but couldn't find exactly what I'm experiencing... so here goes.

First, I'll mention that I haven't performed any work on my brakes in years. So I don't believe it's an issue of installing something incorrectly or not bleeding the air out completely.

My brakes have been fine until a couple days ago when the pedal travel increased dramatically. Whereas before when there was probably ~3/4" of travel until I had pressure, now I have to push it all the way to the floor to feel anything at all. The truck still stops when I push the pedal all the way down (literally to the floor, until the travel is maxed out) but something is definitely wrong.

There are no leaks anywhere and I haven't lost any fluid at all. The brake resevoir is still at it's maximum level. What do y'all think? Master cylinder? What would just go out within a day that would cause me to loose all my pressure and have to bottom-out the pedal before the truck stops?

Thanks in advance for the help. Please let me know if I need to provide more information.

if you don't have any leaks, and your reservoir is staying at the same level... then it must be the master cylinder. You must have failed 1 of the seals inside the master cylinder. So it is leaking, but its leaking back into the reservoir.

The other thing to check is to have someone else apply the brakes and hold them on. Then look at all your flex lines to make sure they aren't ballooned out.

But most likely it is the master cylinder.
Replace it and do a good bleed to get everything back in good working order.