Hello all, I am new to the board. I would appreciate your comments on my issue.

1). I have a Quadzilla monitor so I can see the coolant temp compared with the truck temp gauge.

2). Engine appears to be running cool. Given similar distance to past experience, temp is between 70-90 deg F. where it is normally up to 140-150 deg F by then. No heat.

3). Temp suddenly jumps to 140-150 deg F and continues to increase to normal operating range of 190-205 deg F. Now I have plenty of heat.

4). Run 20 miles or so at highway speed, notice heat is turning cool and temps dropping to 175-180 deg F.

5). Notice temps flucuating from 170-210 deg F. When temps go up, I get heat.

6). All climate controls are fully functional. Coolant is at proper level. Does this sound like a sticky thermostat?

Thanks for any help you can provide.

 

When you say, "Given similar distance to past experience, temp is between 70-90 deg F. where it is normally up to 140-150 deg F by then.", Are you comparing those temps to times when the the outside air temp is the same?

Do you have a winter front or cover on the front of your truck?

These engines will cool down pretty quick when you don't have a load on them. Just coasting to a stop from highway speeds can drop the temp quite a bit.

If you don't have a winter front, I highly recommend making one or buying the Mopar one. I have the Mopar front and helps a lot with keeping things warm.

 

Yes, similar outside temps. No winter cover. It just started with this problem about a week ago. Over the last 2 winters with temps down to 0 deg F, I have had no issues keeping the temps up and having plenty of heat.

 

Your thermostat could be stuck open... But before you go changing parts check your water pump just in case its bad.. just take off the belt and see if it turns freely and it don't wobble.. If so then replace the water pump with a good quality water pump from cummins or dealer (they last longer) If you need a water pump, thermostat, gaskets, let me know via PM with engine Serial number i can get you a price Or you can go to your local Cummins dealer for a price too... if you cant find one or don't know where one is at Cummins.com and it will direct you to the nearest store.