I have a '99 3500 and an '01 2500 that we've owned a few years now. I never seemed to have a problem with the temp's staying at about 170 deg. during regular driving slightly higher towing on hot days. Last year I took them both to an oil change place and had coolant flushes done on both. Mechanic comes out and tells me he put in new yellow coolant and that it's interchangeable with the old green stuff. Since then both trucks run at 190deg plus, and I've been having an over heating problem when towing with the '99.
I had the fan clutch replaced, radiator boiled out, two thermostats replaced and had the fluid checked at 3 different places and they've all said it's fine. I think it's baloney! I've had two 1st Gen dodges and never had them run hotter than 190 on a hot day towing. Even the owners manual say the gauge should normally run left of center. Any help would be appreciated.

 

Mine runs 190F when fully warmed up with old or new coolant since replacing the thermostat with a genuine Cummins part determined by the engine number on the ID sticker on the timing cover.
Loaded, I would expect the temperature to go no higher than 220F

 

My 01 runs above 190 towing, it also runs up around 230 in traffic if it is a good hot day. I don't see a problem with that, electric fans on most cars don't come on until 230 degrees. If they have 190 degree thermostats then they cannot run under 190 degrees. Take one out and put it and a thermometer in a pan of water and heat until the thermostat opens. The temp that the thermostat opens is the lowest temp that the truck can run at. On race cars we used to make plates to replace the thermostat with a hole drilled in the plate to restrict the water flow. This would let the race car run cooler and still restrict flow so it would not overheat. To much flow will not cool and then cause overheating.

 

Just replaced the thermostate to an original Cummins part. I had an original thermostate with 200k miles and had similiar issues. Hell in traffic I had 210 or 220 towing. SO I put a Napa and cleaned the radiator fins by removing it and clean ing with care and I also bought the cummins 180 genuine part and my truck wont see more than 181 on average.
I towed today 10K and it went to 186!

Hope it helps!

 

How in the world do you hit 230* engine temps in NH?
I did a complete antifreeze drain, flush, rinse and 3gal of the 50/50 mix in March08....towing last weekend it was 100*+ and I was hitting 195-200*

 

Don't forget that the stock gauge is good for an estimated range. Unless you guys are using an aftermarket gauge or tuner w/ digital read out the factory gauge isn't really that accurate. I flushed and refilled my radiator/cooling system last year and ran the Delo premix. My temps were slightly below the 190 mark(needle's width) after the flush and have slowly gotten back to 'normal' over the past year. Normal for my rig is just left of center.
I still need to clean the gunk from the puke bottle on my truck but it hasn't ever really been that bad so its a little lower on my list. I'm sure this will help also.
Also, realizing that the radiator is behind the after cooler means that the air running thru your rad. is preheated in a sense and warmer than the outside temps. These engines like 190 I have found out and I don't worry over it too much if it fluctuates a little.

Just a couple pennies, Kurt

 

I also just replaced with a NAPA thermostate and it stays at 180 it was $35 compared to a cummins at $ 75 , i tried one from O' Riley's auto parts { junk } and it vared from 160 up to 230 the tempature was all over the place . Also the NAPA one has a limited life time warranty.

 

thanks for the info guys. I'm traveling and don't get to the computer to often.

 

I had an issue similar to this and almost burned up the motor.

Try draining and removing your radiator. I can almost guarentee it is clogged with oil on the back side. The end of the breather vent tube from the top of the valve cover stops midway of the radiator. The fan clutch draws in all the risudual oil spouted from the tube and it is sucked into the back side of your radiator externally. Once I pressure washed the outside of the radiator and re-installed it, I extended the tube end and have not had any other problems. I did flush and installed a new thermostat also.

 

#1. Drop a meat thermometer in the radiator, it will tell you the engine temp. Start with a cold engine, never do it with a hot radiator.

#2. If you are going to change the thermostat, always take the old and new into your wife’s kitchen, take out one of her shiny pots. Fill it with enough water to cover the 2 thermostats, toss in the meat thermometer and heat up and cool the water to test the thermostats opening and closing temperatures.
New doesn’t mean good, Old doesn’t mean bad.

#3. Buy wife flowers, other wise she'll be upset with you!

 

I fought with an intermittent over heating problem on another vehicle with a gas engine for a couple of years. I changed the thermostats (different makes) I don't know how many times, I took them out and boiled them in pans too. I tried another gauge, I replaced the voltage stabilizer for all the gauges. Did the Rad, checked the timing, and pulled the head for a looksee! All to no avail. Then one evening I'm driving along and it starts to heat up, I think to myself thats funny it seems to heat up as the sun goes down and it starts to cool off. Then it dawned on me it heated up when I put the headlights on. DUH!
Turned out it was a bad ground from the body. Never rule out a bad ground!!!!!!!!!
Not that I think this is the case here.

 

The Gen2's call for a 50/50 ethyl/glycol (green) anti freeze, or Cummins. I am not sure what the yellow stuff is, but would not run it.
Mine always runs a shade over or under 190, seldom sees 200+, even towing heavy in Texas.