is it time for a new t-stat
 

the last couple of days i noticed my engine temp doesn't go above the first line on the gauge. does this mean my thermostat is shot. and where can i get a new one

It could be your gauge, but it's probably easier to start with the t-stat. How close are you to one of these places? http://www.cummins.com/na/pages/en/d...r.cfm?state=OH

razor,

I had the same symptoms - could not get above 140. I opened it up and found this.

T-Bone
https://www.dieseltruckresource.com/...8tstat-med.JPG

make sure you buy the inner and outter seals if they don't come with the t-stat

The picture that T-Bone posted is quite common.
I just remove the rubber ring and trash it, doesn't seem to make any difference with or without it.

where is the t-stat at on a 2001?
my temps move around alot (180-200) ish.