goes there is a overflow port that should have a small 3/8 inch hose attached. Mine didn't go to a recovery tank like it should have. When I shut the engine down the circulation stopped. the temperature climbed exceeding the expansion tank cap setting spring setting and a small amount of fluid escaped down the hose and was lost in the bilge. I ended up installing a recovery tank to trap the fluid. Now, when the engine cools the fluid is sucked back into the engine out of the recovery tank. Could that be your issue?