The Duratec 2.5 liter engine is used in a range of vehicles by Mazda and Ford - Mazda 3, Mazda 5, Mazda 6, Mazda CX-7, Mazda Tribute, Ford Escape, Ford Focus, Ford Fusion, Ford Transit Connect, and possibly others.
They all suffer a common flaw of a plastic (fiber reinforced nylon aramid) coolant outlet bolted to the aluminum cylinder head and sealed with a rubber o-ring. The o-ring and housing both degrade due to heat from the engine and this results in a coolant leak.
This is a potentially fatal flaw as sudden failure of the housing gasket can lead to rapid loss of coolant and overheating of the engine.
The vehicle in this video is a Mazda 5. We use a coolant system pressure system to identify the source of the leak. We show the defective part with a brief DIY tips and tricks for removing and replacing the coolant outlet housing.
