How much of a temp swing on the coolant gauge is normal on cold (20F) versus hot (80F) days? On cold winter days the temp gauge goes to just above the "C" while on hot days it goes just about horizontal. This is about a 30 degree arc on the needle. A $25 OEM temp gauge isn't much but if this is normal it is still $25 wasted. My two thought are.
#1 This is normal.
The thermostat starts to open at a lower temp than when fully open. The low gauge reading corresponds to the temp it starts to open as the radiator is cold enough to keep it there. On hot days the thermostat must be fully open to stabilize the temperature and this equates to the horizontal gauge reading.
#2 Something is wrong.
The gauge variance, if any, should be much less than this. Something is broken or causing the thermostat to always be stuck open a bit. This would cause the engine to run cold on cold days when the thermostat should still be fully closed.
#1 This is normal.
The thermostat starts to open at a lower temp than when fully open. The low gauge reading corresponds to the temp it starts to open as the radiator is cold enough to keep it there. On hot days the thermostat must be fully open to stabilize the temperature and this equates to the horizontal gauge reading.
#2 Something is wrong.
The gauge variance, if any, should be much less than this. Something is broken or causing the thermostat to always be stuck open a bit. This would cause the engine to run cold on cold days when the thermostat should still be fully closed.
