Your fan might be stuck "On" when it should be turned "Off."
First, I would check to see if the fan is kicking on when you start the engine (the fan shouldn't) and then again while you are driving.
Make sure the in-cab switch- if you have one, it's usually labelled "Fan" or "Engine Fan" with settings of "Auto" and "Manual"- is set to "Auto"- Then start the engine.
Open the hood and see if the fan is spinning and listen for a whirring noise.
The fan should be spinning slow enough that you cannot hear it, if it is spinning at all.
If you hear the noise, can see the fan is spinning fast, and the engine is still cold, your fan is sticking on. Check your fuses and circuit breakers- make sure the 2 amp "Engine Fan" fuse or breaker (if your truck has either) has not blown or tripped. The location of the breaker or fuse varies, and it should be listed in your truck's Owner's Manual, Driver's Manual or Service Manual. Reset the breaker if it's tripped or replace the fuse if you find it's blown.
Then, shut the hood and drive the truck. Listen for the fan (a steady whining noise) to kick on while you are driving and note the temperature it kicks on at. On most CAT engines, It should kick on at 200, then shut off when the engine cools back down to 180 or 185.
If it's not the fuse or breaker, or if the fan kicks on and stays on while you are driving, then take the truck to your Caterpillar technician and have them take a look at the ECM settings, fan switch and sensor.