Fiesta Overheating Issue

Sounds familiar. I drive a Fiesta too. Your description sounds like when my map thermostat went bad. The map thermostat regulates engine temperature. Have you checked the coolant level or tested the temperature sensor? These are crucial, and a defective thermostat causes overheating.

Coolant level is fine. I haven't tested the temperature sensor, just visually inspected the wiring. How would a faulty temperature sensor affect the thermostat's behavior? Could the sensor be sending wrong signals, or is the thermostat definitely faulty?

The temperature sensor provides readings to the ECU, which adjusts engine parameters, including the thermostat. The sensor could cause erratic behavior, but given the warm-up time and overheating, the map thermostat is probably defective. I'd have the thermostat checked at a workshop.

That makes sense! I was hoping it was a sensor issue, but you're probably right about the thermostat. I'll book it in at the local garage, though I reckon it will cost me around 350€. Thanks for the insight! I'll let you know the outcome.