So heres the story.. had the truck a week now and when you first get in and go (when it hasnt ran for a few hours and is completly cold) the temp guage will peg out for like the first mile or 2. Then itll drop back down and usualy stay in normal operating temp. So I replaced the sender in the block thinking that might be the problem and it turned out not to be the problem. So now Im thinking change the thermostat? I dunno just brainstorming ideas now to fix it.

 

Sounds like you may have air in the coolant system. Have you recently opened the system for service such as a flush or just to add coolant? Try a 'search' for 'purge+air' and you will find some posts explaining how to get the air out of the coolant.

 

Ah I never thought about air being in the system. Ill purge it and see!

 

So the temp sender and the thermostate wasnt the issue. Also no air in the system. Im stumped