sleepr tsi

I drove my truck about 50 miles today with a good mix of city and highway driving and it never got above (what I guess is) 160. I replaced the t-stat about three months ago when I first got the truck, so it is probably not the problem, although that can't be ruled out. How do I check the fan clutch?

I've never had to trouble shoot a too cool condition before.

schaef_12

How Cold is it where you live? If it is really cold out side it may not get up to operating temp. in 50 miles. Try putting a peice of cardboard infront of the radiator.

sleepr tsi

It's was about 25 when I made the post. I have a sheet of cardboarf coevering the entire radiator already. Sorry, I should have mentioned that before.

lgp9999

Given enough warm up time, it should be physically impossible for any engine to run cooler than the thermostat rating. I'd start by replacing the thermostat and going from there.

JKM

I'd start by taking the fan off and trying it again, you can spin it off and take it out without much trouble at all. If the problem goes away , leave the fan off for the winter.

dssimecek

Might try feeling the top radiator hose, if it burrney hot it might be the sensor or your gage. If just hot or warm, TStat I would guess

lgp9999

I wouldn't remove the fan. It's there for a reason, and you're asking for an over heat by removing it. That would be addressing the symptom, not the problem.

infidel

I've been running fanless in the winter for ten years now.
No problem at all unless the outside temps get over 80.
Even after driving 400 miles in winter temps my coolant temp rarely exceeds 160.
I don't think you have any problem at all.

crane 1

I had the fan off mine for almost two years and 70,000mi. The only time I had a problem was at long stop lights the a/c would blow hot. Even when towing, if I was moving the temp was fine. The cummins has a bypass coolant line that ciurculates even when the thermostat is closed so if you do a lot of highway driving the fan doesn't really matter. Since then I've put 2 electric fans on, 1 for the a/c and one that never turns on with the temp set at 195. for warming up I put a fuel shutoff solenoid on the throttle that bumps the idle up to 1600. works great

JKM

I was addressing the symptom , remove the fan , and see if the problem still exists , if it does , then you have just ruled out the fan. I took my fan off a week ago to see what would happen , I have not noticed any difference at all , except much less noise on start up , as the fan hub will always lock for a few minutes after start up.

sleepr tsi

Thanks for the suggestions, guys. I'll try taking off the clutch fan this afternoon. If it's anything like on my blazer, I'm in for a battle.
I'll keep ya posted

ric o'shea

Reminder the big 36mm fan nut is reverse threads, clockwise to get it off.

SoTexRattler

Try the cardboard trick between the intclr and radiator to help with the warmup. It helps mine with that darned colder 'stat .

If you got the replacement stat from Dodge, you got a "superceded" Cummins stat. That newer stat runs colder than the original (that you can still get from Cummins for 1/2price of the parts from Dodge).
My original stat stuck closed last summer and I was in a real bind. Cummins was out, and would've had to order it from Cummins San Antonio . I had to go to DC and their superceded 'stat DEFINITELY makes Mr "C" run ~160 in the cold.
I've got the "right" (185-190) stat in a box in the truck. After this cold snap, I've GOT to put it in to get the heater to do what it should be doing .

K.

jughead

i submit that the fan and or radiator has nothing to do with the engine getting up to temp. that is the thermostats job only. fan or radiator keeps engine from getting too hot. i have this problem with my 82. even cummins tech support does not have an answer. water coming out of thermostat housing was measured 123 degrees after 20 mile trip on 85 degree day. ps 3 cummins 32.00 thermos in the course of a year.

Mainemike100

You can test the thermostat in a pot of water on the stove. Just drop the thermostat in, put a thermometer that reads to 200 or so in there and start heating it up. When the thermostat opens, read the thermometer and that's the thermostat's temp. rating. If it opens too low, get a new one.

Then, assuming the thermostat is ok, the engine will only get up to that temp. if it is "working" hard enough to produce more heat than is being lost through just radiation off the block, head, etc, and what ever heat is being absorbed by the cab heater. With these Cummins, at an idle if the weather is cold you'll almost never get up to the thermostat opening temp. Got to run at a higher idle, 3rd gens can use the cruise control modification to achieve this. Those of us with older models will have to resort to the brick or stick on the throttle method.