شیر هواگیری مایع خنک‌کننده معیوب

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.