I was traveling up the I-5 this weekend from L.A. to Klamath Falls with no load. I was keeping up with traffic doing around 80-85 mph. Truck ran great.

The problem was that the clutch fan would cycle on and then off. The temp would creep up, fan would come on, temp would go down.

My egt's were good.

I flushed the rad recently, Did not put in new thermosat.
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What do you guys think.

 

I think your clutch fans works

 

It'd be worth it to install a Cummins t-stat...your present one may be sticking just enough to bring the fan online before it (the t-stat) cycles again. Other than that, I'd say yeah, your fan clutch works...wish mine did

 

Working normal.