I am just curious if anyone else has dealt with this problem before. My brakes sometimes go all the way to the floor and do absolutely no braking. The rest of the time they are perfect. This happens anywhere from once a month to maybe twice a day. It seems the same whether the truck is hot or cold. I have replaced the master cylinder, rear hard lines, and all rubber lines. All I can think of is wheel cylinders but I don't lose fluid... Any ideas?

 

No idea. Its like my truck's checkenginelight, works when it wants!! Anyway, the FSM has some trouble shooting in it for almost everything in the truck.

 

Sounds like a possible intermittent vacuum leak in your brake booster. My brakes were scary. Like ˟˟˟˟ your pants scary... replaced the brake booster from a junk yard donor truck. All is well now.

 

The thing is I seem to lose manual brakes a well, not just vacuum assist. Did your pedal go all the way to the floor as well? I just didn't think a booster could fail to the point of complete brake failure, and yeah its pretty scary. Passenger s get kinda nervous when you pump the pedal and mutter "brakes"