its 30 degrees outside and riding down the flat interstate not hauling anything and my coolant temp reads 170 and oil temp is 208. These numbers seem way off what could be causing such a low coolant temp and I know the oil cooler needs replacing because of the huge gap but I don’t understand the coolent being so low

 

In this case I wouldn’t say it’s the differential that says an oil cooler is in the future, but possibly the oil temp compared to expected. That being said, I would expect your thermostat to be faulty and wide open. I would suggest replacing the T/S, and the International/Navistar ones seem to be more reliable then the aftermarket Motorcraft ones, and then see where the ECT/EOT differential is and go from there.

 

You need a new thermostat. I would go with the international part like Jack said over the motorcraft or the ones from parts stores the replacement motorcraft ones don’t seem to hold up very well.

 

Check the temps after a it's been sitting for around 12hrs or longer. You want the eot and ect to read the same. If they're not, could have a bad sensor.

Check the fan speed, your fan could be running wide open 100% of the time. I believe that has to do with the egr valve disconnected. Some egr delete kits come with a plate that blocks off the egr valve hole in the intake manifold and they'll just toss out the egr valve leaving the plug laying there. If you have the egr valve, make sure it's connected. I think that will operate the fan speed correctly.

The thermostat could be stuck open.

It take these trucks a while before they get up to running temps. Take it out for a 20 minute run at around 55 mph before assuming something is wrong. I wouldn't jump on an oil cooler job until I had the temps working properly.

 

Why would his fan be 100% all the time?

I'll also add on the early builds there is a lot of evidence the EGR valve does not affect fan operations