If the coolant is boiling, the radiator hose should be checked by squeezing to see if there is any pressure. What occurred in one instance was after the usual dealer service at 50,000 miles, during which coolant was replaced, the radiator cap was not. Since the old radiator cap seated itself to the radiator, it did not seal as good once reused.

Eventually the driver noticed how the coolant reservoir was gurgling immediately after the engine is turned off, and a smell of burned oil when the car was sitting at stop lights was evident. After feeling the coolant hose it was noticed that it had no pressure. During the two months of driving the failure of the radiator cap never let the cooling system pressurize, and therefore most of the coolant slowly vented out. This created a void in the cooling system that deprived the head and upper combustion chamber of much needed coolant for extended periods of time and numerous heat cycles. Eventually resulting in head warpage and head gasket failure as well as an oil leak which was the cause of the burned oil smell.

If anyone experiences a boiling or gurgling noise when they engine is shut off, it is likely that the radiator cap has failed and is slowly lowering the amount of coolant in the engine. The part only costs $ 6 to replace. It is a 16 lb cap, and can be purchased at NAPA, part # 703-1447, manufatured by Balkamp.