A month or so ago I bought an '08 Aspen, Hemi, AWD with tow package with 42,000 miles to be the family people hauler / tow vehicle for my race car. For the most part it has been great. I replaced the shocks with Bilsteins and added Coil-Rite airbags for towing.

Over the weekend I towed for the first time with it. I tow from sea level over a 4200' pass back down to the track at about 250' elevation. Leaving very early in the morning, temps weren't issue and everything went well. Coming home yesterday afternoon with temps in the 90s and it was a different story. The trip home has a much steeper grade to climb and it definitely tests the cooling systems of cars. My water temp gauge climbed up to 3/4 mark even with the AC off, windows open, heater on and going about 40 mph. I haven't found much info about these engines overheating so maybe it's a simple fix.

My friend tows the same trailer over the same pass with his 05 GMC Sierra 5.3 with 4 speed trans, AC on and going closer to 60 mph. I've towed many times the same pass with a 98 4Runner towing an open trailer in hotter weather with AC on and going faster and the temp gauge never budged.

Since the maintenance of my Aspen is questionable, it seems be be in good shape but I have no records. I changed the engine oil/filter and air filter so far. It might need a basic tune-up and some fresh coolant but any ideas would be great. Thanks.

 

More than likely your elevated temps came from the heat being generated with the transmission. Were you using your tow/haul mode on the trasmission? And, try a little more speed. That would help the air flow thru the radiator. Also make sure the coolant is in decent shape by testing it. Let us know back what you find out.

 

Could be your thermostat. I had to replace a thermostat at 30,000 miles. Good thing it was still under warranty.

 

Sorry it took me so long to see these responses, thanks. I talked to my friend with the Sierra and his water temp goes up in the same spot so it probably isn't an issue. I've towed another time going to the same track and had the same issue. I doubt it's the thermostat because I would think the gauge would climb in more places if that was the case.
I have a question out to a friend who has a Ram 2500 with Hemi to see if his water temp rises significantly in the same place.

 

I have the same issue that you do. After a lot of research, here is what I've done and where it sits.

I've drained and replaced the entire coolant system, and have a new thermostat and radiator cap. Also cleaned out the dirt/bugs from the radiator. The Aspen still runs hotter than I think it should when towing up a grade (basically no change from before).

My next step is to replace the fan clutch. If that doesn't work, then the last option is to go with an aftermarket upgraded radiator.

There are a few posts on this and other forums (check dodge durango forums) that seem to indicate that the stock radiator has issues handling the heat generated by the big engine when towing. I'm fairly certain that I'll have to end up replacing the radiator with a bigger/more efficient one.

I haven't had any luck finding a bolt-on bigger radiator solution yet. Hoping I don't have to go custom.

I have an 07' Aspen 2WD w/ Hemi & towing package. My trailer is 29' & 5500 lbs dry. I tow from Vegas (2250' elevation), and have towed over 8000'+ passes. I have to watch the temp very, very carefully - occasionally turning the A/C off. Only had to turn the heater on twice. Most of my heat management is done by ensuring the RPMs stay in a manageable range (below 3300 ish) - using the Tow/Haul feature and a steady right foot.

 

Thanks Mongoose. Let me know if you find a larger capacity radiator. That really does seem like the issue.

On another note, have you looked into the larger transmission oil pan? I believe it's a popular mod for the Durango guys that tow. Just adds transmission fluid capacity.