95 GMC Brake Pedal to the Floor
 

Hello all...Here's the deal...

95 GMC Sierra, 4X4, 4.3L V6, 5-Speed, ABS, Disc Font, Drum Rear.

Here's the deal...Truck driven once a week...got in and started...put foot on brake pedal to shift into gear...pedal felt fine for two seconds, then to the floor we go!!!

Brakes still work...barely...checked for leaks...none found...

Checked Master Cylinder fluid...dirty, but OK...

With truck turned off, brake pedal feels fine...turn on engine, pedal to the floor...BRAKE light on constantly...turned off engine...brakes pump up and feel normal...turn on engine, pedal to floor...

Checked MC again, small, front resevoir empty...checked for leaks, none found...replace fluid...same symptoms...no idea where fluid went...

Any ideas out there?

Skully

Could be the master cylinder itself, watch and see if the rear resevoir fluid increases as the front decreases. Also see if you can tell if there are any signs of fluid leaking between the master cylinder and brake booster.

bleed the brakes, then see if you have built any pressure. if not then you have a hole in the line or a fauly Master Cylinder or ABS module

Thanks for the help, guys...sorry for the late reply, but been out-of-touch for several days...

After an intensive inspection of the brake line systems, a very badly corroded section was found in the rear main brake line up under the frame rail, hidden by the fuel tank, after the truck sat for a few days...took some time to find the seeping fluid...Open your eyes, man!!!

Purchased some replacement brake line from the local parts store and replaced entire run from front to rear...bled system and everything seems to be operating properly...gotta love those easy fixes...

Thanks again for the replies...forums such as these contain great information...

Skullbones