OK, every once in a while my temps shoot to the red zone (factory gauge). It only happens in city driving, and once I get rolling it goes back down to normal. Strangely enough it happens more often when it's cool out. This is very intermittent but it's been driving me nuts. Ideas?

 

Maybe a stopped up radiator,water pump, bad gauge, or sticking t-stat, since its only happening in traffic at slow speed i'm leaning towards the radiator. Also have you noticed any coolant leaks near the front of the truck.

 

is it loud sounding? maybe the clutch fan is not working right????
have you had the rad flushed out lately? maybe you need to do so, or if it was done there could be air in there.
t stat could be sticking too, how clean does the rad look in the fin area?

 

Rad looks clean, and I don't see any fluid leaks, BUT, I do seem to lose coolant and have to keep topping off the tank. Fan works fine, but it does sound loud when this happens. I was thinking stat, maybe I'll start there and see what happens.

 

The reason its loud when that happens is the fan is kicking into high gear to cool the engine (212* is usually when it kicks). Also temp sensor might be out its right next to the t-stat. Let us know it goes.

 

Is the stat & sensor cheaper at a Cummins dealer?

 

I know the t-stat is a lot cheaper at cummins, I got my temp sensor at dodge though. Would sure check at cummins first on the temp sensor.

 

Lack of air flow thru the rad and heat generated in the transmission tends to drive the coolant temps up in the situation you described.

Put a manual gauage on it and watch the swings in coolant temp in differnet driving situations. P{retty interesting to see how much fluid coupling can drive coolant temps and how much the factory gauage covers up.

 

yeah take the checkball out of the trans line. like these guys said it could be a lot of things fan clutch t stat radiator cap etc check the gauge first and then youll know!