when my truck gets warm it gets up to like 240 and holds for a while and then goes back down to about 195.I have a 180 thermostat in the truck
I also removed the thermostat and ran with out it. It got up to about 190 or a little below. it took a while to get there but stayed there for a while.

any ideas?

 

https://www.dieseltruckresource.com/...s-t275274.html

 

Uh.....240* is way to hot. WAY TO HOT. Is your fan working? Can you hear the roar of the fan? What makes it go up and what makes it go down? Have you noticed that it goes up while in traffic but not while driving down the freeway, etc.

I read the thread regarding temperature fluctuating but I think its bogus. Never has my thermostat fluctuated like that or anything like that thread said. Sure I hear some 12v's will do that some but the 24v temp gauge should not move but a hair. If it doesn't want to warm up and tends to stay cooler in the winter then you have a bad thermostat. Overheating can be a bad thermostat too but usually thermostats are designed to fail in the open position so you can still drive. I'm guessing that your radiator is either clogged up with oil residue crap from the engine vent catch bottle or your clutch fan is no longer working.

 

The fluctuating thing is on the first gens, not second gens. Easiest thing to do is go to a dealer and get a new OEM thermostat. Lots of threads on it. Most common solution is an OEM thermostat.

And as KATOOM says, clean out your radiator. Might want to delete your puke bottle and redirect your crank case fumes down below your axle. Costs about 6 bucks to do.

If your radiator is really dirty, you really need to take it out to clean it right. You can rig up a spray nozzle with some 1/4" copper tubing on the end of a hose and some degreaser, but the best way is to take it out all together. It is kind of a pain, but you will be amazed how much gunk is in there.