I own a 2000 Dodge 2500 with the Cummins.............it needs a heater core.......again............it'll be the 4th one since it was new. I've had it with this crap......the heater cores are $200.00 and the labor is $375.00 to install. The first one went out when the truck had 55000 miles, the second one made it another 20000 miles before it went out........they always go bad when it starts getting cold. I was told last year that I needed to add some conditione to the radiator so I did. It's supposedly electrolosis or some crap that keeps eating holes in the cores. Is there a good stop leak product out there that might seal this thing up for a while. Every year it happens right before Christmas. I also wonder if this is more of a diesel thing or just the newer electronic junk that causes this to happen. It's funny how you could run an old Chevy in the ground but the heater never quit working.