I have a 1999 Saturn SL with 75000+ miles. When I got in to my car I press on the brake and the brake peddle went clear to the floor. I pumped it once and got the resistance back. I released the parking brake and backed out, went about 25 yards to the street and stepped on the brake, the peddle went clear to the floor again. I stopped with the parking brake. I drove home and when I got home the brakes worked fine. The brake fluid is fine and no leaks and the brake drums weren't hot to the touch when I got home. What could cause this problem?
Only 2 possibilities.
One, a leak in the hydraulic system allowing fluid out and air in.
Two, a bad mastercylinder.
I vote for number one.
How far was the ride home?
Where the front wheels warm/hot?
If I had to guess from what you desribed. I would take a close look at the rear wheel cylinders. Out of sight and out of mind. Pull the drums and peel the rubber cap on the wheel cylinder back. If it is wet inside it leaks. Rebuild or replace. Do both sides even if you only find 1 side wet.