Rogue Overheating Engine

Overheating and coolant spills are never good. A control unit communication error could definitely be the culprit if it's messing with the cooling fan operation or the thermostat. Have you tried scanning the car for diagnostic trouble codes (DTCs)? That would be the first step. Note the exact code, it will help pinpoint the issue. And are you able to check the coolant temperature sensor readings with a scan tool or other diagnostic tool?

Yes, I scanned it and it pointed to a communication fault in the data link, but I'm not sure what that means exactly. As for the coolant temperature, where do I check it and what should the values be?

A communication fault in the data link suggests a problem with the wiring or connections to one of the control modules. It could be something as simple as a loose or corroded connector. The coolant temperature sensor is usually located near the thermostat housing. The exact values vary, but an unusual value while the car is cold or operating points to the sensor itself. Given the 'communication fault' and overheating, I'd carefully check the wiring and connections to the engine control unit (ECU) and any related sensors first. In your case, with the coolant leak and overheating issues, I'd suggest consulting a trusted mechanic.

Thanks, that's helpful. I'll double-check the wiring and connections. As the issue might be difficult to solve, I will probably take it to the workshop. Turns out it was a defective cable or plug connection of the component. Repair set me back 95€ Appreciate the advice!