Engine Overheating

what size engine? 5.3? also, have you verified flow through the radiator? you already replaced t.stat, so next get the engine hot.... (operating temp around 215degrees) and grab the upper radiator hose... is it hot? next reach down and grab the lower radiator hose. (engine off) is it hot also? if not, then your not getting flow through the radiator... i understand you tried to flush it... this doesnt always work. let us know your results.

It's a 4.8... Will definitely check the hoses tomorrow! Thanks for the reply!

no problem... i look forward to hearing back from you.... also, keep in mind this vehicle from factory with dexcool-its orange... dont ever mix with green, as it will clump up, and clog everything....

Checked both hoses this morning... Flow is good... Not sure at this point what else it could be. Any more suggestions?

how long does it take for it to start to overheat? and does it overheat at idle, or when your driving? you verified flow through the radiator, my next guess is that its airbound.... when you turn the heat on, does it blow hot air from the vents???

Sometimes it overheats at idle and sometimes it does not! The heat does not blow hot when turned on. We are thinking there is air in the system. Does this sound the same to you. If so, what is the best way to get the air out?

no heat from vent verifies my suspicion... it is air bound.... let me check to see if this engine has an air bleed screw.... i dont think it does, but im going to double check.... have you checked the coolant level after you initially filled it up? also, does your radiator have a cap, or do you fill your vehicle through the overflow tank?

After initially filling it up it settles and the coolant is a little lower but not empty and the truck does not have a radiator cap. We looked for an air bleed screw and either the truck does not have one or we did not find it.

This is starting to sounds like a blown head gasket can you run a check?

https://www.2carpros.com/articles/head-gasket-blown-test

I will get a kit and do the test and get back to you. Thank you SO much for your help. We are going to try this and I will get back with you. Hopefully with good news!

no problem... im looking forward to good news!

I have the same exact issue with my 2005 tahoe 4.8 I have done everything from replacing the radiator to the ect sensor and to the cap. I also pressure filled the system to ensure there was no air in the system but still I'm having the same overheating issue with a constant shut down when the truck gets hot. Please help!

@ Nicole Graham... It ended up being a slow leak at the quick disconnects to the rear air that became a pretty steady leak. We replaced numerous things, had compression tests done, etc. No one including us could find anything. It ended up being those disconnects. We replaced them (a $25 part) and it immediately stopped.