2000 123Kdisco is now doing another odd thing. Temp gauge, which has been rock solid center for past 60K (my ownership) now dips low to bottom of operation range (within brackets, not to cold) and drifts around between center and there. I'm thinking sending unit, thermostat. Any ideas - am I in any danger?

Thanks

 

Thermostat is most likely stuck open... bet it takes a good drive to start warming up too? Does it blow cold air through the heater?

Stuck open is less of a problem than stuck closed... but stuck is still stuck. Replace as soon as you can

 

Thank you, Sir. Finally, something that doesn't sound like $500!

 

First go check and see if your coolant bottle is completely full, if not fill and bleed it cause you may have air trapped in the system and the temp guage can't read the coolant temp.