Hello all,
I recently picked up a 1987 S10 Blazer and I'm having brake issues. My pedal goes to the floor while the vehicle is running, however while it is off I have all the pressure in the world. I have replaced the master cylinder, brake booster, vacuum check valve, and both rear wheel cylinders. I have bled the system and I know for sure that there is no air. Has anyone else had this problem and if so how did you solve it? I'm at a loss and the only other part I can think that could be bad is the proportioning valve. Thanks in advance.

 

Does your year have ABS brakes? If so, there could be an issue with the ABS system not being bled correctly. Just a thought.

 

It does not have abs, it's too old.

 

Id look for a vacuum leak in the power brake system.