my 2000 4runner has an intermittent problem with the brakes that only happens right when the car starts and only after it has been sitting overnight . the problem is simple, the brakes just don't work and it is quite scary to be backing out of the driveway without brakes. when this happens the brake pedal still has 100% resistance so it's not like i can pump the brake pedal to build pressure. i'm thinking there might be a problem with one of the valves from the brake system but i'm really not sure so any input would be great.

thanks

 

How cold is it when this happens?
When was the last time you changed your brake fluid?
Brake fluid absorbs water, could it be that ice forms at thelowest point in your system? Not reallty sure, just brainstorming...

 

i'm in colorado so it gets pretty cold. most likely it's been below freezing every time it has happened and i havn't changed the brake fluid since i've owned the car. what you are thinking sounds plausible to me. any other input?

 

I'd change brake fluid at least yearly, that stuff absorbs water.