It my quest to find my headgasket issue a while back I tried a few different radiator caps to see if it made any difference at all. I tried 7, 13, 16psi caps, the universal kind and also an old 100kps and new 120 and 140kps german caps. No difference with any of them. I am running the 13psi cap now. Runs fine, no overheating, etc.

The main reason for pressurizing the cooling system is to increase the boiling point of the coolant. IIRC, 15psi coolant boils at 265*F? That is a large increase and a nice wide margin of error/extra capacity when running the engine at 190*F. So at 13psi I don't have quite the safety cushion the a 140kpa (22psi) cap would provide. I also don't have the extra stress of 22psi on the multitude of old parts in the cooling system. Why stress things if you don't need to?

RT

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