Ford Ka Overheating Coolant Leak

Sounds familiar! I had a similar issue with my Ka a while back. Overheating and the check engine light are definitely not fun. When you say 'control unit communication error', can you be more specific? Any codes showing up? It could be a faulty sensor messing with the cooling system or something with the CAN bus. The coolant leak probably means the system is seriously over-pressurizing.

Okay, the diagnostics tool spits out a generic 'control unit communication fault' message and no other codes. I suspected it was the CAN bus at first but I have never seen such issue. Any idea where I should start looking?

Ah, a generic fault! That's less helpful than it sounds. In my case, it turned out to be a dodgy connection in one of the plugs going into the control module. Check the wiring harnesses and connectors for any signs of corrosion or damage. Honestly, though, if you are not 100% sure, the best bet is to take it to a workshop and let the professionals have a look. They have the diagnostic tools to pinpoint the issue quickly. My mechanic found the root cause in a couple of minutes.

Thanks for the advice! Took it to a local mechanic, as you suggested. Turns out you were spot on – it was a corroded connection in the engine control unit! They cleaned it up, replaced a short section of wiring, and it’s running like a dream now. Cost me 95€, which I'm more than happy with. Cheers!