My temp gauge goes up n down
 

My 95 12v cummins thermostat goes up normally but runs midway between red and normal running temp, then it drops slowly to below running temp. No unusual sounds, runs like a champ. truck bone stock. accept a rebuilt tranny with towing and some power in mind 350-400 range. 1 piece 5 inch 0.125 walled alluminum drive shaft. 5 inches from the turbo out. Nothing under the hood except removed silencer ring from turbo. Could sensor be bad and where can I find it? The coolant in the rad is so clean is like theres no flow, any input would be greatly appreciated. :choochoo:

major fluctuations in temp seems to be the norm for these trucks, there is a "improved" thermostat that is supposed to help......I think there is even a part number posted in a thread here somewhere, but the general consensus is, it seems to bother the driver not the truck.

my truck does the same would like to know more about that thermo.

My truck was doing this too, but it is winter here in MN so I put cardboard in front of the radiator and it doesn't cool down as much now. Helped out incase weather isnt a factor for you.

Thanks
 

I was hoping to hear something along those lines. Like I said the truck seems happy to work, and hard. :rocking:

Just make sure it has a cumins thermostat in it.

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My 98 12 valve does the same thing, the cummins upgraded thermostat should fix it, but there's no reason to do it right away. Wait until you do your next rad flush. The stock one works just fine, witha big rad, it cools down really fast in cold temps.

Corb

cummins part #3928499