I’ve fitted a Metro engine to my Mini, and now there’s no bypass hose on the head. Someone has mentioned to me that the coolant won’t flow around the engine until it gets warm and the thermostat opens. Would I be able to just drill holes in the thermostat to fix this issue? Or is there another, better, solution? Ratty
Yes, that is quite correct. The bypass hose is there to facilitate coolant flow prior to the thermostat opening, particularly when the heater valve is closed off. Coolant circulation is imperative at all times to avoid localised overheating, especially around the combustion chambers. This is exacerbated by the temperatures reached around the exhaust valve seats. Drilling a half dozen 3mm holes around the periphery of the thermostat is any easily solution to the problem.