On Sunday, my car started to over heat. Popped the hood and notice that the small tube (no thicker than a pencil) that was connected to the radiator (near the cap) had popped off. There was some coolant on the fan and floor of the car.

Connected the tube to where it originally came from and thought the issue was fixed. No, car would still over heat. Did not drive rest of sunday

Yesterday (monday) morning i opened the hood and unscrewed the radiator cap and found that it was not topped off. Resevoir tank was full though. Monday afternoon, i topped off the radiator and drove the car around for about 10 minutes. No over heating problems.

This morning I took off the radiator cap and found that it was no longer topped off. Topped it off again (not as much coolant needed as night before) and drove it to work. No over heating.

Absolutely no signs of leaking anywhere, resevoir tank still full, exhaust is not emitting white smoke, no check engine or man't required light on.

Thoughts?