Check to see if water is circulating by looking into the radiator. If it is, it's probably not the water pump. Overheating was an issue when I bought my truck. No one could figure out why. I discovered it wasn't circulating. Pulled off the water pump and found there were no impellers, they had rusted off. Replaced with an Advance or Autozone with lifetime warranty. No problems since (10 yrs. ago)