I'm pretty new to these petrol engines but it seems to me that all of these systems consider temperature as part of the engine management system. So I would quickly check all electrical connections to as many of the thermostats you can identify as possible!

I would then also see if you can read any fault codes from the engine management system - these days the car has some way of telling you what is wrong.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!