Random lower coolant temperature

[howardc64]

01 V70XC 100k miles. Last coolant change at 60k along with thermostat.

Been chasing a really low level coolant leak somewhere and haven't found it. Put in fluorescent dye and don't see anything yet. Looked above and below the engine as well as the pipes going into/out of the heater core. The coolant reservoir isn't moving much recently so maybe the leak stopped.

The bigger mystery is.. why does my coolant temperature gauge show lower than normal temperature randomly by say 1 tick mark on the gauge. It never goes above normal (about middle of the gauge) What would that indicate?

Been holding off the coolant flush until I find the leak.

[billr99]

01 V70XC 100k miles. Last coolant change at 60k along with thermostat.

Been chasing a really low level coolant leak somewhere and haven't found it. Put in fluorescent dye and don't see anything yet. Looked above and below the engine as well as the pipes going into/out of the heater core. The coolant reservoir isn't moving much recently so maybe the leak stopped.

The bigger mystery is.. why does my coolant temperature gauge show lower than normal temperature randomly by say 1 tick mark on the gauge. It never goes above normal (about middle of the gauge) What would that indicate?

Been holding off the coolant flush until I find the leak.
Corrosion at the connector between the harness and the sensor, maybe? Differences in humidity and/or temperature along with a bad connection could explain the intermittent nature of your reading that you are seeing.

Good Luck,

Bill

[howardc64]

Found this problem. Read in another forum, a Volvo tech suggests

If engine temp gauge read lower than normal and you have weird cabin heating temperature problems... then likely the thermostat.

Changed my thermostat and bingo... everything is back to normal :) I guess the old one (<30k miles) must be been stuck open frequently.

Lets see if the low level coolant leak is related. I'll report back.