This morning after about an hour's drive I was stopped at a light. My wife points to the temp gauge and says - should that gauge be so low ? It was like around 150. The light changed and when I accelerated the gauge went back to normal. When we got home I checked the coolant overflow - it was fine. There are no leaks. We replaced the radiator about a month or so back. Does this sound like the thermostat ?

 

Did it jump straight back to normal temp after you accelerated or was it a slow build back? If it was a quick snap back to operating temp I would guess you have some sludge in the coolant system creating temporary blockages.

Did you flush the system when you changed the radiator?

 

If it were blocked it would overheat not drop in temp.


Check the connections at the sensors for starters, clean and reconnect wait to see if it happens again.

 

I was thinking blockage traps coolant in the heater core and it hits the temp sensor cooler than the rest of the coolant. You're right though, for that to happen the blockage would have to be past the Tstat housing and that seems unlikely.