dumbo;1325286 said:Couldn't it be a small leak in the hose from the oerflow to the rad? Allowing air to come in on cool off?
Yes or clogged line. The radiator-to-overflow tank has a specific ebb-and-tide like the ocean and the moon. When it HEATS, it expands and "fills" the overflow. When it COOLS it draws back from the overflow into the radiator. This is a balancing act. IF the hoses, cap-to-overflow, radiator cap, tubing IN the overflow cap, etc, etc... are compromised -OR- you are otherwise drawing AIR instead of VACUUMED COOLANT back from the overflow on cool-down contraction, you will end up with some of these symptoms.
Just some thoughts...
-crisp