I recently lost breaking power from my power brakes while on the road. Now, before taking action, I have this question: how to find out if it's the power booster or the master cylinder. With the engine off the brake pedal is solid, but with the engine on the pedal goes all the way to the floor with no braking action. The car is a 69 bird; I was sure it's the master cylinder, but now I better ask! Thank you guys.