Brake problem

[KBOI]

I need some help with this one, folks. I have a brake problem.

06 extended cab, 4x4, 4.0, automatic. 79,000 miles.

The problem: The brake pedal will intermittently go to the floor with very little weak braking pressure at the bottom of the pedal travel. It started happening yesterday morning, it was very cold (4 deg). It did it a few times and then it seemed to be fine the rest of the day. It did it a couple times this morning too (it was 14 deg). I really have no idea if the temp has anything to do with it, it just started when the cold air moved in.

I checked the brake lines front to back and there are no leaks. There is no leak at the back of the master cylinder and the fluid level is fine. There are no "ABS" or "Brake" lights lit on the dash, and no ABS codes stored in the computer.

The master cylinder seems to pass the old test of slow, easy pedal pressure building pressure at a reasonable pedal height.

Anybody have any ideas about solutions, or further diagnostics I should do? I just don't want to start firing the parts cannon. Thanks for your assistance!

 

[1990RangerinSK]

I'm just guessing here, but I'd say check your pads (front) and shoes (rear) for proper adjustment, and wear. If your fluid is fine, that would be where I would start. If your pads and shoes aren't overly worn, and they are properly adjusted, the next place I would look is the master cylinder. As far as I know, if it's bad, the whole thing needs to be replaced.

Good luck!

 

[Andy D]

Maybe apples and oranges. In warmer temps than yours, VW bug MCs would fail internally when they reached a certain age. Only in cold weather. Never in warm weather