cooling system
 

Hi All, I have a question about 93 diamante. First thing in the morning when car is cold, I took off radiator cap and start the engine. The coolant level immediately starting rising and it was overflowing. It was not big overflow but drop by drop overflowing. and when I rev the engine to about 2000 RPM and coolant was being sucked back very little and it stopped overflowing. As soon as I let it idle at 600-700 RPM it again started overflowing but slow and steady. I don't have overheating problem. thermostat replaced recently. Sometimes I see some small amount of steam from radiator fins and car is at normal operating temperatures. Any inputs?