Coolant Level - BMDUBYA
Apologies for my ignorance.
Car is eight years old over 100k. If fill the coolant level up via the expansion tank and you overfill, I assume that the excess will drain out and via the overflow pipe when the car gets going. Now the question I have is.

1. If you over fill your coolant, will this cause any damage to any engine parts, gaskets etc, whilst the excess is draining off? If so why have the overfill/flow pipe?

Thanks in advance

Coolant Level - John S



(b)to make sure the answer to (a) is No. The cooling system is designed to run at a pressure above atmospheric, so raising the boiling point of the coolant above 100C. This ensures that (especially in hot weather) if the coolant at some points in the system gets above 100C it does not boil and produce a vapour pocket which will cause overheating. (Steam does not conduct heat away like liquid). However, with any pressurised system it needs a safety valve, and the pressure cap and overflow provide this - it allows excess pressure, or overfilled coolant to escape, so preventing damage. It also caters for the really bad problems of gasket failure, and prevents hoses being burst.

John S
Coolant Level - BMDUBYA
Thanks John, very detailed answer, just what I was hoping for. If only I could have asked this last night, before I was trying to pump out the coolant at 11.30pm, standing on my drive in the rain wearing latex gloves with a manufactured hand pump made out of a, cleaned household disenfectant spray bottle, and a washing up bottle to catch the excess. (I know coolant is very poisonous). :-)


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