2003 2500 4x4 Hemi 121000 miles Automatic leveled 33x12.50x17 No Mods

Ok, having an overheating issue. Truck runs fine but after 5 or 6 miles of run time (enough time to get to around 210, i'm assuming this is the half way mark on the old idiot temp gauge) the temp will continue climbing to about 3/4 or further on the gauge. Most times as long as I'm at highway speeds and not stressing the engine the temp will remain at that level but if i'm making the engine work a little, say a light load (1000-2000lbs) or on a hilly road then the temp will get too hot and i will have to cut the truck off to cool down.

This doesn't happen everytime I drive the truck but it does occur quite often. My initial reaction is a thermostat that isn't fully opening but I'm not sure. I have flushed the coolant already which seemed to help for a couple of days but the issue has reappeared for several days now. I also checked the fan (not sure if this is the correct way to check it though) I grabbed the fan blade and tried to spin it hard assuming that if the clutch was bad that it would spin freely and if it was ok that it wouldn't turn much at all. Please correct me if i'm wrong here.

 

when you changed the fluid did you run a descaler through the system? is there debris in the rad..have you washed the rad out? Have you burped all the air out of the system?

 

yes to descaler, no to debris, yes i washed it out. How do I know that all the air is out?

 

My normal MO when I see an overheat issue is to first burp the system to assure there are no air bubbles in there. If that doesn't fix the issue, then I remove the thermostat and test it for proper operation by bringing a pot of water to boil with the thermostat in it, then allowing it to cool, making sure the thermostat is opening and closing properly.

After that, it's time to look at hoses, the radiator, etc...

 

We have a How To on burping at the top of the section in the FAQs. I would replace the stat as cheap insurance. We have a thread in there also on Thermostats.

 

Yeah i found the how to after i replied. Actually I've already done that guess I just wasn't under standing the term is all. After I hooked all the hoses up and filled it with coolant I let the engine get up to operating temp with the cap off. I'm going to do it again though this afternoon just to be sure that there isn't additional pockets.

On a side note, all the hoses felt firm (ie they shouldn't be collapsing) and there is no leaks any where in the system. I have changed the radiator cap and have inspected the radiator for bent and/or clogged fins.