At least it was an $11 part, my Cummins started losing coolant a few weeks back, turned out to be this little tiny freeze plug (approx 3/8" dia) located at the back of the head right up near the firewall. Dealer tried twice to order me one, local diesel shop had no luck finding the correct one, ended up having to buy a box of 10 from napa for $4.10
so a $.41 part had my truck parked 
. At least it was a cheap fix, because it sure wasn't fun or easy 
