Vanne de dégazage du circuit de refroidissement défectueuse

The valve venting air from the cooling system into the expansion tank, faulty so gas cannot separate out of the coolant. Air in a cooling system is the enemy of circulation — it collects at high points, forms locks that stop flow, and makes temperature readings meaningless because a sensor surrounded by air reads air.

On electric and hybrid vehicles this matters more than on a conventional engine. Their circuits are low-volume, have many high points, and cool components with little thermal mass, so a small air pocket stops flow to something that overheats quickly. The complaint is a component-specific over-temperature with a full coolant tank, which is a confusing combination until the air is accounted for.

Distinguish a faulty valve from a system that is simply full of air after a repair. Any circuit opened and refilled needs bleeding by the correct procedure, and many require a vacuum fill because gravity will not clear the high points. A system that fills correctly and then accumulates air again has a genuine fault — either this valve or a leak drawing air in — and that repeated accumulation is the evidence worth gathering before replacing anything.