I know this is a Mazda6 forum, but I have the Mazda6 2.5L engine in my 2010 Ford Fusion. It has a just turned 6000 miles and is sitting in the local Ford dealership waiting for a new replacement engine. The problem started with the sound of coolant flowing through the heater core (air entering the cooling system). There were no other symptoms--no overheating, loss of coolant, etc. Only low coolant pressure. After a few trips to the dealer for cooling system purging, running tests, etc. a field engineer came and evaluated the car. The head was removed and apparently there was porosity in the block cooling passage between #4 cylinder and the outside of the block. I haven't heard of any engine problems with the 2.5 and wondered if there was anyone with a 09 or 10 Mazda6 that has had an issue like this. Thanks for your input.