I was just wondering where about the temperature reading should sit when up-to running temp, currently mine reads like this (slightly more in traffic):
Mine sits in the middle of the guage when running and moves to about 3/4 when stuck in traffic then the fan kicks in and it goes back the 1/2 way.
How old is your coolant and what colour is it?
Drain your water and flush the system well out. Top up with enough coolant and water and take it from there. Why not change your oil and oil filter while your at it. I had the same problem in my old Polo S. A good flush out and plenty of coolant solved the problem.
same as mine i would say.
goes about 2/3 the way up the gauge when in traffic then bang on in the middle when travelling over 40mph.
no sense changing the sensor, just change the coolant as a precaution and see how it goes.
as whiteshark says it would be worth doing a service while you are there
The temp sender could be at fault. As the temperature increases there should be less resistance to ground. When you start the car up from cold does the gauge move up a fraction right away?
Yes worth a coolant change if you don't know the history, the blue stuff is best replaced every 2 years.
£7.99 for ready mixed coolant and it's enough to do the whole system. http://www.eurocarparts.com/ecp/p/car-a ... &0&cc5_865
If you can remove the thermostat as well and you can test that's ok by putting it in boiling water and check it opens, it should open at 88 degrees C, you will need a replace the seal when removing the thermostat. http://www.eurocarparts.com/thermostat-housings-gasket