u know what, my accord was doing a very very similar thing.

when you bleed the air out of the cooling system you need to crank the heater. well my heater cable came off the valve thats in the cooling system so i could never bleed it.

What my car was doing was boiling the water into the over flow and the overflowing it, it would then suck the remaining water back into the system. It would do this over and over and the over flow was always low.