I have read a long discussions about the check valve between crossover pipe and radiator bleed pipe and which way it should be installed. There seems to be a lot of doubt if it was installed the “right way” in the factory. I have ordered a new valve EAC4168 and it looks like it is actually designed to be installed the way that check valve “ball” is facing the crossover pipe, as it will not fit the other way around. It looks like that Jaguar wanted it to work the same way as thermostat jiggle-pin. It should let the air out but stop the coolant flow when there is no more air. But apparently in real life it doesn’t work as intended and people have better experiance with check valve ball facing the radiator or without the check valve at all. In this case air and water can flow from the crossover pipe to bleed pipe but not the other way around. This setup made more sense to me as there will be constant flow from the crossover pipe to bleed pipe when engine is cold and should help to bleed the engine better when the engine is cold. When the engine is warm, thermostats are fully open and there is no coolant flow from the engine through crossover pipe to water pump, the check valve will prevent the coolant from being sucked by water pump the other way around. So I decided to modify the new check valve as per pictures below:
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