On the gauge the needle does not get beyond the 'block' on the left (20% of
max), driving for half an hour in traffic with outside temp between 5 and
10 degrees C. Is this long enough for the needle to get to the middle?
There is plenty of heat from the front and rear heaters.

I have ordered a new thermostat, but could it be the sensor itself that is
at fault? Is it worth getting a new sensor?

For a brief time after changing the coolant, the temperature did swing to
the middle and back. Can I assume this was just due to an air bubble which
has burped itself out - the radiator bleed screw lets out coolant.

Secondly, and almost certainly unconnected, the red LED in the middle of
the gauge does not flash even if you pull out the wire going into the
expansion tank. Is this normal?

Thirdly, I have also ordered an expansion tank pressure cap just to be safe
- is this too paranoid?

Lionel Tun
84 GL, 183k miles
lionel@ark.prestel.co.uk