Just to add to my earlier suggestion, but I still could be barking up the wrong tree!
I don't know if the 1.8 engine is similar to my 2011 2 litre. On mine, there is a temperature sensor screwed into a multi-piped “cooling flange” (not to be confused with the housing for the spring loaded stat, up front) which is awkwardly located at the rear of the cylinder head. It sits under the air filter and coil pack and as well as several large bore and small bore pipes there is a cable connector which attaches to the sensor.
I discovered this when I had to change the housing last year as it was weeping coolant.
This sends signals to the ecu to control fan and other things that may affect engine temperature like mixture etc.
If you have one of these, it may be worth first inspecting the wiring for damage and also pulling the plug to make sure of no corrosion.
The sensor itself is a replaceable part (ebay) as it is a brass body screwed into the plastic body of the “cooling flange” and may be about £10-£12.
Worth a try if all else fails?
Last edited by Deejay; 31/08/25 03:34 PM. Reason: changed wording to coolant flange
