I bought a 2004 Vectra 1.8 petrol a week ago and have funny temp readings. In the morning the temp gauge rises up to around 82f but only after driving on free flowing roads for a good 15 minutes. Even when I get on the motorway on the way to work I will do 35 miles and gauge sticks to around 82f. However if on any part of my journey I remain stationary for say a minute the gauge will quickly rise to 90f but no further. Once I get up to speed again in free flowing traffic it takes the car a good five minutes for he temp gauge to return to what I assume is the normal running temp for this car of 82f. I spoke to Vauxhall servicing the first day I get the car after getting to work. The guy said this seems normal but to pop out on my lunch hour and check coolant level. I did and this was right on the correct level. He then said start the car and leave it running for a good ten minutes until temp rises no fn kicks in. I left car running for 20 minutes and the gauge reached as high as 90f but would not o higher than this. As it only reached 90f which is well short of the red zone my fan never kicked in. This has been the pattern of the reading on the temp gauge for the pat week I have had the car. However last night I got in my car and after completing my 30 minute drive the temp gauge did not even move a mm. It was if it was not working. Leaving the car to tick over this morning for ten minutes the gauge appeared o be working again and reached 90f. Coolant level shows tht I am not loosing any fluid. The heater in the car appears to work okay. I felt the top of the radiator and this does not get warn unil several minutes of the car running which I believe is correct. The thermostat housing and pipe from it o the radiator get very got after a few minutes which I guess is Wht it should do. Looking at the coolant water bottle there is a thin pipe which goes in at the highest point on the bottle to the thermostat via a metal pipe halfway. Water appears o be going into the coolant bottle via this pipe when warming up. Is this normal? Was going to change thermostat but it not want to this if it is okay and likely o be a sensor. What if the previous owner has constantly topped up coolant bootle o the point the antifreeze has been very iluted. What this make a difference. Thanks in advance for your help.