Radiator Fan failing to work
If you notice the water temperature suddenly rising when you get stuck in a traffic queue, it may be that your radiator fan is not working.
This is a common cause of over-heating engines - the failure of the radiator fan to start as the water temperature rises. A wide range of things can cause this, but if your radiator fan is not working, it is worth checking the temperature sensor connector. The connector contacts are prone to getting dirty.
To test the connector itself, you will need to remove the engine access-panel under the rear parcel shelf. Remove the retaining clip and start the engine. Then pull off the connector from the sensor. If it is only the connector failing, then the engine speed should drop slightly and the radiator fan should start. If this happens, you will need to spray the connector pins with a suitable electrical contact cleaner.
Use a proper electrical contact cleaner such as Electro-lube etc. from Maplin , Farnell or RS, etc. Do NOT use WD40 or CR5-56 or any similar products.
One other aspect worth considering is that, dependant upon the amount of driving you do, the front fan may actually very rarely be used. This can lead to it being stiff and requiring a much larger than normal starting current, sufficient enough for it to overload and blow the 15 Amp fuse. You will not know the fuse has blown until you start seriously overheating, with the danger of blowing the head gasket !
The recommendation is to upgrade this fuse to 20 Amps.
Better to be safe than sorry.
For details of adding a visual / audible alarm for water over-heating, go to Alarm - add Water Temp and Low Fuel