I'm driving a 2001 bluebird freightliner Cummins 6 cylinder diesel. It weighs a little over 17,000 lb empty. We're driving through Kentucky up and down the Hills on I-65 midday and the engine is fluctuating between 200 and 220 degrees. 220° up hills and 200 degrees going down Hills . Check the fan it's running fine just had it serviced by a mechanic before we left Iowa. Ran all night in the cool weather perfectly fine. The current temperature outside right now is 90 degrees. I've been keeping it at a fairly steady 65 miles an hour. Am I running it a little too hard? Should I drop down to 55 miles per hour?
Pulled over to a flying j waited 30 min engine dropped to 170. Drove 1 mile and it shot back up to 200. Pulled off to a Walmart waiting an hour to cool. Anyone else have this problem? Should I worry?
Pulled over to a flying j waited 30 min engine dropped to 170. Drove 1 mile and it shot back up to 200. Pulled off to a Walmart waiting an hour to cool. Anyone else have this problem? Should I worry?

