What puzzles me a bit is that many people use these same arguments regarding engine coolant systems. When coolant heats up it expands so it's normal that coolant on a closed system is pressurised raising the boiling point. It's normal that the upper hose on a warming engine is hard. There is a 2 bar cap on the expansion tank for a reason. The coolant from the lower hose is cold (colder) if the radiator is doing its job or the thermostat is not yet open and there is no circulation thru radiator because the engine is still in warm up phase.

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E39 530dA -02 M-Sport Messing metallic
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E70 X5 40d -12 M-Sport Space grey