I'm trying to replace the heater core in my 01 Durango and am having trouble locating all four nuts inside the engine compartment. I found the first two pretty easily and then a third behind the transmission dipstick but can't find the last one. The Chilton's and Haynes book don't tell where they're located only that you have to remove four from the engine side and one from the dash side. It was a pretty frustrating weekend since I completely removed the dash and everything only to have to put it all back together without replacing the core since I needed the vehicle to get to work. I'd like to try and finish it this weekend if possible. Any help would be greatly appreciated.