Vectra 2002 Temperature - paulvm
Having problems with SWMBO's 2002 Vectra 1.8. The heater has stopped working (not good as weather has changed!), and the temperature gauge has gone crazy. It goes up to the edge of the red sector then down again and then back up again.
Obviously something is not right! Have topped up header with 1.5 litres of water, so could be a leak or air lock. No obvious signs of leak or of mayonaise in the oil, so hoping head gasket is ok.
Mileage is 66,000 and serviced per schedule by the way.
Any ideas please?

Value my car