[GCP4]

I Just bought a super clean 98 Eldorado ETC. I put new antifreeze and a thermostat in in right away. The car runs great but everyonce in a while at a light the temp gauge will go to the next line after the half way point. I Know these northstars pretty well. I've owned a ton of them. Im 98% sure it's not a headgasket issue. Im think radiator. Any Ideas??