Engine Temp/Thermostat Question

[MAYoung]

Gentlemen:

I installed a new thermostat and water pump in my 5.9L Cummins last winter. Upon starting up, the engine temp ran up to about 180 degrees F instead of the usual 190 degrees F. I thought that the cooler temps of winter might have kept the temp down but now that it is a warm June, the temp has not moved past the 180 degree mark. I assume that this is ok but would like to hear your thoughts.

Thanks in advance, Mark Young

 

[NIsaacs]

I would leave it alone. I run oem 190 t-stats in my '01 for years until last year when I went to a 180. I really like it and think the truck does too. Just my opinion, but I think the extra 10* causes all kinds of issues. I have 330k miles on my '01...one head gasket, two water pumps, two alternators, tappet cover gasket, resealed the vacuum pump twice, one rear main seal...all heat related, I think. My '91 also has 330k, all of the above items have never been done on it. It has had a 180 all it's life.

 

[Rich Poirier]

My truck runs better on a 180, especially if you have a "power-adder". Have had no problems. And then, I took the advice of TDR and removed the radiator to clean all the "gunk" from the oil-catch can that had accumulated over the years. That made a huge difference, thus complimenting the 180 thermostat. I couldn't believe how plugged up it was. Simple green worked well for that. Purple Power not a good idea as it could attack the aluminum core. Then opted to remove the "pill bottle" and ran lines (including a crafty oil vent tube I concocted for the oil cap) VERTICALLY down past the axle a little bit. I saw minor mileage and power increases with the little bit of elbow grease it took. The radiator was literally black everywhere outside the circumference of the fan. During the summer months, it drastically reduces fan clutch activation, especially while towing. I realize this is a little more than you asked for, but these little things kinda go hand in hand. It was well worth doing.

 

[Cummins12V98]

Guessing NOT a Cummins T-Stat.

 

[B.G. Smith]

The 180* was what my 99 came with.

 

[DavidC]

The 180* was what my 99 came with.

Mine to. And replaced with another Cummins 180

 

[MAYoung]

The replacement thermostat was a Cummins part supplied by Dodge. I ordered the only part number that was listed by Dodge.

I am going to leave it alone. The thermostat prior was OEM that came with the new truck Changed it simply because I did not want it going bad on a trip. It had nearly 263,000 miles and 21 years.

 

[AH64ID]

The 190° will be very slightly more fuel efficient, which is why Cummins made the change.

If you tow heavy and often the fan will now come on too late, and you risk running hotter than you should with a 180° thermostat, which is 212° max per Cummins. The 190° thermostat isn’t full open until 207° and has a max a 225°. You can see how you could be above the 212° but only barely where the fan comes on.

 

[BigPapa]

Just FYI, these are the current Cummins numbers for '94-'02 models:

• '94-'98 - 3928499, 180*
• '98.5-'99 - 5292742, 180*
• '00-'02 - 3946849, 190*

 

[Cummins12V98]

Normal driving in 70 degree weather my 01 stays at 190 to one needle thickness below 190 with the Cummins stat.

 

[KATOOM]

Whatever you choose, I wouldnt suggest running a 180* thermostat in a 24 valve if you live where the average weather is cooler. Its fine if you live in a warmer climate but not where its colder. This is because the 12 valve came out with the 180* as the two valve heads retain more heat therefore can run a lower temp thermostat. But the 24 valve heads run cooler due to the added air flow which means they dissipate combustion chamber heat faster and require a warmer thermostat to maintain optimal combustion chamber temperatures. So you can see where driving in cooler climates would have a negative affect on a 24 valve running which has a cooler thermostat.
Note... Some '99 trucks came out with the 180* thermostat because Dodge/Cummins hadnt discovered the cooler cylinder head situation until about a year after the 24 valve trucks were introduced. Thats when they switched to 190* thermostats.

 

[Rich Poirier]

I agree with Katoom. I live in upper cental Arizona at 5300 ft. A pretty mild and arid climate. It is a benefit here, yet may not be in a cooler and higher humidity levels. Although, it could be that higher humidity levels might exaggerate heat, what do you guys think? Also, could the lower 180 help in keeping the auto trans a little cooler? I'm curious to what you all may have experienced. I have a 2001 24v auto btw, manufactured in late 2000. I specifically went to a lower 180 from stock 190 because of the Banks Big Hoss. More fuel creates more heat. So far, so good. I will say this, it is fun and eduactional to dabble with the workings of a diesel engine vs. a gas engine. Gasoline engines being more predictable and straight forward. Diesels tend to be more influenced by the environment, or weather-picky if you will. Good day to yas.