Mercedes GLC Diesel Engine Trouble

Sounds like a potential CAN bus connectivity issue. A faulty control module can cause all sorts of weirdness. The overheating and coolant spill could be related to a sensor not communicating properly, causing the cooling system to malfunction. Have you checked for any obvious signs of damage to the wiring harness near the affected control modules? What error codes specifically did the car diagnostics report?

Thanks for the quick response I haven't checked the wiring harness myself, I'm not really confident doing that. The car diagnostics report said something about a 'control module communication error' but didn't give a more specific code. Is checking the wiring harness something I can easily do myself, or is it best left to a professional?

Given the symptoms, I strongly suggest bringing it to a workshop. A connectivity issue or software glitch within the control module could lead to further damage if not addressed correctly. The CAN bus system is complex, and without the right tools, you might cause more harm than good. Plus, overheating can quickly escalate. Don't risk it.

Okay, that makes sense. I took your advice and brought it to a workshop. You were right, it was a defective connection to the control module. They replaced a faulty connector, and the total repair cost was 95€. Thanks for the help!