DieselBoy20

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?

RPM1

No, you will not see the optimum fuel economy but you should be fine for a little bit.

For the most part they fail open. Obviously if it was stuck shut it would be a much different scenario.

infidel

Your temps are totally normal. Instead of a new stat put a load on the truck like it was designed for.

What the dealer was supposed to tell the buyer of 12 valve trucks when they were 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.

In 1998 they changed the electronics for the coolant temp gauge due to customer complaints. The engine temps are still the same except now the gauge lies to you.

DieselBoy20

Well you learn something new everyday, just thought these trucks stayed at 180 at all times like my 07 did and my 12 does. Good to know...