I remember there was a time my heater core leaked coolant so the radiator would get low on coolant sometimes. I kept the overflow tank filled up so the radiator could suck coolant from it, but one day it didn't take the coolant from the tank so the radiator got a little bit warmer than usual.
The hose worked most of the time but for some reason (old age, bending) it sometimes wouldn't allow the radiator to suck coolant. I changed the hose for a more durable one and no problems since.
