My coolant gauge hovers right around the 30% mark while driving, but from what I have read it should be steady at 50%. If I sit in traffic or am idling for a while it does reach the 50% mark, but cools right down again when I start driving.


Is this normal? or should it be holding steady at 50%? Also, ambient temperatures are about 20F where I live right now.

 

The three things I'd focus on first are a) the engine coolant temp sensor (ECT) b) the thermostat and c) the gauge. Since you say it eventually gets to 50%, I'd wonder about the thermostat first. Has it recently been replaced? Its possible a prior owner dropped in an after market brand with a lower opening temperature. Does the car run ok otherwise - ie no check engine light, normal gas mileage etc? If you want to fix, you can replace both the thermostat and the ECT at the same time - just make sure the thermostat goes in the right way and fits properly with no gaps.

 

Thanks for the reply, I ended up replacing the thermostat and all is well now.