Internal. Not like old timer spring with disk.

The needle on e53 is nearly pointless it shows about a 40° C swing in temp as "perfectly fine". No indication it's about to overheat until it does.

Usually the overheating will be caused by the reservoir or hose blowing.

If you shut down within minutes of a venting situation you likely caused no damage.

The problem is when the coolant how's the sensor will be often be dry no longer measuring anything useful just the steam blowing past it.

The idiot gauge that's pretending to be a thermometer is really a 3 position idiot light.

1: ice cold
2: warm, normal or hot
3: way too hot should have shut down five minutes ago

I drove my poor car for four months in open loop when my thermostat failed due to the moronic design.


–awr–

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)