New to diesels-overheating and a/c prob.

[rpbfixit]

Just joined this site and it's been very helpful. I bought my first diesel about 6 mos. ago.2008 250 SDD XLT 6.4L 4x4. I LOVE THIS TRUCK! 2 Questions-The engine has been overheating while I'm driving in town but as soon as I get on the hwy. and hit 60-65mph. it immediately goes back down to normal. Coolant level is right and have had all fluids checked, two oil changes with new fuel, air, oil filters. which leads to quest. #2. When I bought it [with 183,000 mi.] I replaced the "main" belt and a/c belt because the a/c belt was squealing. It is doing it again and my a/c is only cold when I'm on the hwy. First diesel, I need help. thanks

 

[dtsinc1]

I would check the fan clutch. May not be locking up at low speeds.

 

[Dogman]

Sound like the fan is not working. Do you hear it kick on. You would know it if it does. It get real loud. There is 4 bolts on the top fan shroud two on top and two on the side take the shroud off and check and see if the fan is plugged in. The fan is electric and some people don't plug them in all the way.