Coolent gets abnormally hot

[Theeonyxblackgmc]

Hey i need some help with my truck its a 2018 GMC Sierra 1500 5.3 L gas engine my engine coolent temp gets ip to 243 when getting on the freeway and sometimes just going up to 60 i have replaced my coolant tank reservoir my radiator my coolant tempature sensor my water pump and my thremostat a couple times to try to fix this and even after all that it still gets hot im thinking it might be an air bubble but not sure if someone could please help me and give me a some advice that would be great i dont have money right now to take it into a shop to figure it out and yes my fans work ac works and hot sir works. But if some could help that would be greatly appreciated! Really just have hit a road block i cant get past.

[newdude]

Start out cold, take the cap off the tank, let it warm up for a few minutes.  Then hold the throttle open to about 2000-2500rpm and have someone watch the coolant tank for the level to drop.  Hopefully once it hits the 195-210F mark, if there is air it should start to burp the level down.  

 

If no coolant drops or the temp keeps climbing, idle back down for a minute or two and shut it down.