In the summer my 97 water temp gauge cycles up and down like normal but in the winter it never even gets to 180. I put a piece of cardboard in front of the radiator with a hole in front of the fan clutch (so it thinks it cold and doesn't engage) and that doesn't help. Heck I even had the cardboard in all last summer and even towing it never gets near hot, just normal cycling from like 200-170 or so like the TSBs explain.
Now that its getting cold out again its never getting up to normal temp and therefore the heater never really works great. Do you think the thermostat is sticking and never fully closes? If so what brand of thermostat is best? Napa, Dealer, etc?
Mods are in my sig and it has 197k.

 

I went to Cummins , but it seems they sell a cooler temp [ about 165*F ] than what was in it before [ 180* ] .
So I would ask what temps are avalable and get the 180* .

 

I don't think there is anything you can do about it except use your heater in the recirculate mode.
In the Montana winter I've found you don't even need a radiator, just the heater core is enough to cool the engine especially when sucking outside air.

You can try removing your fan completely, I used to do it back before global warming made our winters warmer but haven't done it for several years.
It does help some. I was able to leave my fan removed from Oct to May with no problems as long as I wasn't towing heavy.

Never found winter fronts or cardboard to help at all.
Changing the stat doesn't help either since very little coolant is flowing though the radiator when it gets real cold.

 

My truck wasn't getting warm either. The stock thermostat has a piece of rubber that comes loose and gets caught. It keeps the thermostat from closing completely.

Looked like this:
http://www.mvdirona.com/TechnicalArt...ateFailure.htm

 

I agree with Bill...I'm so sorry that I throw my orginal t-stat out...I have tried two different cummins t-stat and same thing....Blocked off the whole rad hasn't helped...I'm going with the fan removal now..Now my truck is under cooling and smokes more because its not up to operating temp....Not good for the motor...

 

Take a look at: https://www.dieseltruckresource.com/...elt+%23k080694
post # 33 & 38 ( in page 3 )

Mike

 

That's very inventive, using a shorter belt to bypass the fan pulley.
Never thought of that one.

Easier to remove the fan on a 2nd gen though.
After you've done it a few times it takes less than a couple minutes start to finish.
Nothing needs to be removed except the fan if you do it by pushing back the upper radiator hose, pull the fan up so the oil fill is between two blades then rotate the fan clockwise.

If you're leaving the fan off for a long period store it standing upright.
If you lay it down flat sometimes the oil slowly drips out.

 

Got my fan off and removed all the cardboard...Running the so called slow opening t-stat from cummins which has a lower operating temp but will elimate temp flucuations.Which it didn't get rid of the flucuations.