That's the brakes.

I was going to take the El Camino out for a spin and as I backed out of the garage I applied the brakes and the pedal went to the floor. I checked the fluid and added some but nothing changed. I got the car back into the garage without any problems and went to NAPA for another master cylinder. When I got home I remembered the problem I had when I first changed it. The replacement has a push rod hole much deeper than the one that's on the car. I brought it back and another should be here in the morning. I may have to replace the booster some day too.