Fixing all your keys
AO Silver Member
Join Date: Mar 2001
Location: United Kingdom
County: Tyne and Wear
Re: engine temp fluctuating bt 80 110 quickly
A quick change from 110 to 80 sounds like the thermostat is sticking, but if you then get a quick change back from 80 to 110 it sounds like the gauge is sticking and you are getting false readings.
If you only get the 110 to 80 movement happening mainly it can be that the first phase fan is not functioning correctly. Try pulling and reseating the fan relays (near the battery). Sometimes the relays start to get bad contacts as they are in quite a hot position on the V6, just like everything else!. This makes the first phase fan not switch on at 90 (you can also check this by watching the fans but it never does it when you watch!). It could also be the resistor sensor on the top rear of the radiator as these do rust easily.
When the second phase fan comes on the temperature drops very rapidly indeed - faster than the temperature sender can respond, so it looks like an instant drop on the guage.
That happened to me so I`m telling you the story, but it does sound like the gauge or the thermostat in your case.