I have a 04 dodge 3500 with 5.9 diesel with a automatic trans. Noticed today as I was traveling through some hilly roads pulling along about 12,000 pounds behind me the temp gauge rose quickly after the trans dropped out of overdrive/lock up.. It went to the top end of the scale but then as I crested the hills and the trans shifted the engine temp gauge dropped back down to normal within a mile. Never did this before so I checked the radiator , oil and trans fluid. All were they should be. Now what could cause this to happen.
Sounds like air in the cooling system to me. Should use a vacuum filler to be sure to get all the air out with today's cooling systems with very small openings in the radiator and heater core, easy to have air trapped in those during refills and cause those problems.
I used to fight that problem until I started using one.
