So i have an 03 350 and i did the motor swap a couple months back and been having issues ever since i swapped a non rev up into a rev up and ever since then ive had an “overheating” issue the temp gauge says it’s hot but its not actually hot i’ve changed out thermostats, temp sensor l, flushed it etc. multiple shops have looked at it and said the engine is not getting hot but the temp gauge is well when u did the swap i did not change the ecu or flash it or anything and i did not change out the harness either is that my problem or is it something deeper than that? another thing is when u take the thermostat out and run it open it runs fine but as soon as i put it back in it “overheats” i’m not leaking coolant no blown headgasket i’ve burped it for hours, so did a shop and nothing. what do i need to do?

 

but an 03 isn't a RevUp?!?!? Am I missing something?

Purging all the air out of cooling system is notoriously difficult. Almost ALWAYS the problem when "Overheating"

Explain why you think your 03 harness and ecu is RevUp.

 

Drill a small hole in the thermostat at the top

 

why do you think i put this in here. i don’t know exactly why i’m asking i have no clue if its rev up or not but i know the manuals are rev ups so figured it was a rev up my fault i said it was a rev up dawg

 

been tried that i’m not as stupid as i seem apparently i’ve done everything a shop would do at home nothing has worked.

 

well you did state RevUp in non-RevUp........but sounds like you got A DE aka non-RevUp. so you should be good.

Keep bleeding......research all the 'Tricks" on here and you should be good to go.