I just helped a buddy replace his TJ radiator. Tried out my new radiator fill/burp bucket out for the first time. Spill free and the easiest way to let the cooling system purge itself of air. There may be others like this unit that are better, but this worked fine. His cooling system was all new except for the radiator. New radiator dropped it 10°. No visible signs of malfunction, just all there was left that wasn't fresh. I knew we could get it cooler.
https://www.amazon.com/gp/product/B01I40ZQWE/?tag=wranglerorg-20
https://www.amazon.com/gp/product/B01I40ZQWE/?tag=wranglerorg-20