Is the thermostat at fault? it takes a good 15 miles for the needle on the temp guage to rise to 80, then drops off then back to 80 and stays put is this normal ? my other vehicles warm up and stay within the middle of the temp gauge and dont drop back down. From engine cold the heaters within the car warm up quick but gauge takes ages to come out of the blue, no coolant leaks and all seems fine. I have replaced the cts as a matter of course but still the same?
My other vehicles Ford Focus and good old Smiley face Transit, temp gauges seem to hit centre in a matter of minutes after setting off from cold, but not the Vectra. notsure.gif