Overheating

Did you purge air out of the cooling system? Disconnecting the heater coil will not make it run cooler.

Same thing happened to my 2011 Frontier Mech. said it was heater core/coil. they replaced it and it fixed the problem completely. Cost $1500 though.

If your dealing with a 3.3l non super charged that is a water cooled intake manifold there is a small screw above idle air control valve loosen screw half its length run engine up to around 2000 rpms for a few seconds an let idle until you see coolant bleeding out around screw tighten er up good to go

I love all these answers I've read an they don't come no where close to what has to be done to fix problem just like the replacing every thing vehicle still acting up an electric part you replace on a first generation Xterra frontier you have to do a hard reset on the ECM engine control module (computer) remove ground hit brake pedal for about 5 seconds then remove positive cable let it sit all night in the morning put positive cable back on wait 30 minutes put on ground then fire it up good to go actually there supposed to be hooked at a dealership to there setup to reconfigure the hole set up but good luck with that first generation any Nissan dealership can't hook up to it cause it's to old