[ReelMagic]

Not sure if this helps but as the engine warms up and the coolant expands its normal for the coolant cap to allow coolant to go to the overflow tank. When the engine is shut off and cools down it normally sucks the coolant from the overflow tank back into the engine.. Ensure your cap is correct for the motor and not failing... If the coolant doesn't go back into the engine and you need to add coolant after the engine cools down I'd suspect an air leak somewhere and or the heat exchanger (could be the oil cooler as well)... Ensure the thermostat is seated in its housing correctly as a failed or not seated thermostat could cause the water flow to partially bi-pass the engine when running high RPM. M2C