2015 1500 Eco Diesel Overheating after driving an hour on highway

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Paul Thorson

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Rowlett, Texas
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2015
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Eco-diesel
My truck runs great for an hour, but after that on the highway, it overheats at any speed over 65. The heat starts in the oil and spreads to the Coolant Temp and Transmission. I had an issue with the transmission last year and the part that allows the transmission to cool was replaced. Cooling fan seems slow to come on, but this was in nice weather, not summer heat. If I keep the speed at 65, all is great.

I'm not real savvy on engine work, but it seems like this might just be one part that needs replaced.

Temps at 75 mph after an hour inch up to 226 -coolant, 219-transmission, and 231 -Oil Temp. Oil is the first one to get up there. They came down after slowing speed down to 65.

Any ideas would be helpful.
 

crash68

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how's the coolant level? Did this come on all of a sudden or has the temps gradually crept up? Has the EGR cooler been updated via recall?
 
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Paul Thorson

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Not sure about the temps. I don't take that many two hour trips. It does take an hour on the highway for the temps to get up there.

I am up to date on all of my recalls.
 

huntergreen

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Since I don’t know much, I always start with the simplest possible solution. Is your thermostat working properly?
 
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Paul Thorson

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Yes. I replaced the thermostat last summer. I did not get it at the dealership, so I might start there. It does seem simple.
 

GTyankee

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Would that fan modification help ?
from the 6 cylinder
 

crash68

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Would that fan modification help ?
from the 6 cylinder
No, the EcoDiesel is already equipped with a 850 watt PWM controlled electric fan. It's power is direct from the battery via a 100 amp fuse. Ram started using the same capacity fan on the Hemi in the DT body trucks.
 

crash68

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It does take an hour on the highway for the temps to get up there.

I am up to date on all of my recalls
If your at freeway speed the engine should pretty much up to temperature even when the ambient is 40°F. I wonder if the t-stat is not closing all the way and hanging up and not opening.
People have noted that the engine temps seem to run cooler after the AEM update.
 
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