So the other day i was just driving through traffic and my g started steaming (2008 g37 coupe). I immediately pulled over and popped the hood and saw coolant leaving from the heater hose (the coupler had broke.) I replaced the coupler with a metal one to prevent future problems and tried to drive. Still no luck and it overheated again, when i tried to restart it it sounded like the engine started chopping like only a few cylinders were working, and i could not go past 3k rpms (put the car into limp mode). After doing some research i found that there is a good chance it could be the thermostat, so i bought and installd a brand new one. Started up just fine and seemed to be idling and keeping a good temp, sure enough right as i got onto the main road the temp started to skyrocket so i turned back to my house before it could start steaming again. Anyone have any clues as to what it could be? Sometimes when i start it up it sounds like a diesel engine too.

 

Did you bleed the air from the system using a spill free funnel? These cars are notorious for trapped air which causes overheating.

 

No i didnt bleed it, just ordered a bleeder port from z1, should be here in a few days itll replace the other heater hose connector (which doesnt have a bleeder port on it)

 

Almost definitely needs to be bled. Lisle spill free funnel would probably be better than the bleeder port I would think too.