As the temp here in the south started getting warmer this summer, my Durango followed suit and began running warm as well. During normal driving with the A/C on, everything was normal but when I went through a drive through a busy drive through or was in stop and go traffic, she would run warm. Long story short, I changed the water pump, thermostat, electric fan, and flushed and refilled the coolant. While I was in there I noticed that the radiator fill was cracked so I ended up replacing the upper hose and radiator fill / cap. She seemed to run a lil cooler but still warmer than she should. I suspected that the new radiator cap was crap and bought a Stant from Advance. It seemed to fit better but not as firmly as I remember on other vehicles I've owned. Again, things seemed to improve but she still threatens to overheat in 90 degree plus weather with the A/C on. If I turn the A/C off, no problems.

Yesterday I drove on the highway for 3.5 hours on the highway at 70 MPH, A/C on, and 80 degree weather with no issues. When I pulled into my driveway I could hear the coolant boiling. I've checked the fan clutch and it seems to be just fine. I'm not losing coolant, the replacement e-fan is working, and I've replaced just about everything but the radiator and the fan clutch. The fact that she stays cool as long as she's moving leads me to believe that my issues are being caused by one of two things, either my fan clutch is indeed crap despite how it seems or I'm still having issues with the damn radiator cap holding pressure.

Has anyone here have issues using non-Mopar radiator caps? Has anyone here had issues with fan clutches seeming OK but still not working as designed? Any good ideas would be extremely appreciated. I would really rather not continue throwing money at the issues hoping to find the one part causing me pain.

 

If you have a 4.7, you need to burp it to get rid of trapped air in the rad lines.

 

According to the manual I read you're supposed to elevate the front of the Durango and release the air at the upper radiator hose connection at the engine. I did this twice when I replaced the water pump and flushed the system but I guess i could do it again.

 

Yep, you have to elevate the allen key bolt near the upper hose area where it connects to the engine. The engine should be warm and flowing. What you do is gently turn the bolt until you hear air escaping from the bolt. When you see fluid/coolant seeping from the thread, then you would have burped the system. Just retighten and you're done.