My son was driving our 2010 impala police with a 3.9 last night when the car ran hot. He pulled off the road and we had the car towed home. I ran the car around the neighborhood this morning and the temp stayed normal. I opened the hood and on the top of the radiator on the far left hand side there is a nipple that looks like it should have a small hose hooked to it that is dribbling water out of it. Should a hose be hooked up to this nipple or what? Any help would be appreciated. Have never had a overheating problem before on this car.