Got this message twice this week. Should I check the res when car is cold, or hot? Temp gauge does not go past the halfway point when driving. Is there a propper way to top off the "dexcool" other than popping off the cap and filling it to the "full" line?

 

I had the same thing happen a couple years ago. I had a small leak in my radiator which was covered under warranty.

 

Check the res...I get that once a year or longer. I simply add the OEM fluid since it drops maybe a 1/2" below the full line.

 

'Check it', when it's stone cold . . like first thing in the morning . . but, after coffee.
When the coolant cools down and the pressure reduces, coolant will be drawn out of the reservoir to the engine. The cold reading check will be more accurate.

 

Probably a radiator seam leak. If you have warranty, have it replaced and change surge tank cap annually. Top off cold.