If all the above fail to solve your problem.

What brand is it? Alot of people have trouble with non-Cummins thermostats.

 

Running a NAPA heavy duty, and no problems yet.

 

Well.. I tried a Autozone crap, then Advanced Auto, I now have a Carquest heavy duty, it doesn't have the little air holes in it, but it seems to be working. It's a 195 degree t-stat. I know, it's too hot, I'll have to ordedr a Cummings one. I got the air out of my system by firing it up, and jacking the front end up in the air, it worked, silly, but it worked. What degree t-stat do I need? 170 or 180? I'm not sure on how to get one directly from Cummings, I will have to look around on-line. As always, you guys (and gals) are great to me with your endless info. I appreciate all your help.

Thank you
Billy D

 

I had the same problem after a flush and new coolant. I thought it was the thermostat right away so I got one from NAPA. It didn't help, turns out it just had a little air in the system. I cracked the hose clamp on the heater line and bleed some air out there. It works great now.

 

your going to want a 180 degree thermostat. thats a stock one

 

The Cummins part number is 3802968

Just call your local Cummins shop.