Nissan Repair: 2000 xterra overheating, blown head gasket, head gaskets

Question
My 2000 xterra was leaking so mechanics changed radiator, noticed that the new leak after that was no where near the radiator or waterpump. Did pressure check found new leak/crack on heater core hoses, replaced that, week later truck starts to overheat again. Mechanic says only other thing it can be is intake gaskets because he can see green gunk/residue around intake. But there isn't a leak no more that's visible, just that the car overheats. Noticed that coolant was low,but no puddles of water or coolant or wet spots under hood. Truck has 125000 miles on it, mostly ran on water and not coolant from 2004-2009.

Answer
Edgar,

Either you have a blown head gasket or you have a leak.  If this mechanic cannot perform a pressure test to verify would lead me to go to another mechanic.  Basically, they pressurize the system and check for leak down.  If the system leaks down then the intake could be probable.  If you want to see if the head gaskets are blown use a bellows system to verify if there is carbon monoxide in the coolant.