Okay so I noticed a small puddle under the truck one day and thought it was the AC. Then yesterday I noticed the temp gauge at 3/4 so I pulled over and turned it off and walked to buy some coolant. I have an apparent leak somewhere but can't tell where its coming from. Its dripping under the passenger door. When looking up from the bottom it looks like its coming from the firewall, running down and dripping by the door. It leaked out about a gallon in 6 hours. Any ideas what this could be?