My 1996 12 valve isn't getting to operating temperatures coolant wise, it only gets to about 70 degrees celcius and should be running around 95, and I believe the thermostat is stuck open which means I need to put a new one in. I bought a new one but I don't have time to get it put in right now due to having to go away to work right now. What my concern is right now is will I hurt anything running it like this for a little while till I can get the thermostat swapped out?

 

Diesel engines naturally run cool, your temps are just fine.
My rigs only get to to 95C (200F) if I'm towing a very heavy load uphill.

This is what dealers were supposed to tell buyers of these trucks when new:

NOTE: THE COOLING SYSTEM USED ON THE CUMMINS DIESEL ENGINE EQUIPPED VEHICLES PROVIDES THE CAPACITY AND PROTECTION OF THE HIGHER GVWR AND GCWR RATINGS AVAILABLE ON THESE VEHICLES. OWNERS SHOULD BE ADVISED OF THE NORMAL SLOWER WARM UP AND LOWER ENGINE OPERATING TEMPERATURES ASSOCIATED WITH DIESEL ENGINES.

THE COOLANT TEMPERATURE GAUGE WILL FLUCTUATE ON DIESEL ENGINE EQUIPPED VEHICLES. IT IS INFLUENCED BY VEHICLE LOAD, OUTSIDE AMBIENT TEMPERATURE AND EXTENDED IDLE TIME. THIS FUNCTION IS CONSIDERED NORMAL

GAUGE FLUCTUATION WILL BE NOTICED MOST OFTEN UNDER STEADY STATE (HIGHWAY) DRIVING.
PLEASE ENSURE THAT YOUR CUSTOMER IS AWARE OF THIS NOTE PRIOR TO RELEASING THE VEHICLE.

 

Hi DieselBoy20,

I have same thing and was also told to replace it with a new one but have yet to do it. The only time I want it hotter is in the winter, the heat output even with a front on is less than desired. I may change it for a hotter runner thermostat b4 winter.
Is heat output an issue with you as well?

 

Its blowing good heat I believe, haven't had the truck to long enough yet to run it in colder weather to test the heater core, but also am thinking of putting a cummins 190 degree thermostat in it anyways to make it run a tad hotter

 

thanks for replying twice to both of my threads infidel, muchly appreciated