Im thinking my brake master cylinder is going. When I start the truck the brake pedal will go down but it will go all the way to the floor but the brakes are still working and there are no fluid leaks and there is enough fluid in the system. Then when im driving sometimes when I push the pedal down it will go down like its gonna go to the floor the its like the brakes realize they're supposed to be working then they kick in with the force it would normally have with the pedal halfway down then it will just randomly lose pressure again. They always work even when the pedal is all the way down. Any thoughts on what is going on?

 

You have air in your brake lines. re-bleed the brakes.

 

Take the Master off and bench bleed it, Then bleed all 4 corners. Also just check the wheel cyls in the rear

 

^ This.

 

The master is 50 bucks after core, if it comes off replace it.


I have a booster flake out on me, squishy pedal then mega hard. Almost had no brakes. Turns out the booster had a tear in it, so it would boost until the tear opened and dump all vacuum. At that point it felt like the floor but it really wasn't.

So I replaced both of them, and the soft lines. Massive improvement, feels like the truck is new.

 

It was actually the rear brakes, the shoes were bare metal. Replaced them and adjusted them now it's fine