Ok so my heat stopped working while idling and would only blow hot when I was on the gas. Couple days later (11-17-2016) was sitting at a light and my car started to overheat. Pulled over immediately got it towed to my friends shop. Replaced the radiator that blew and the thermostat. Still no hot air unless holding rpms at or above 2k and now while it idles it's fluctuates not by much and it doesn't die but around a 200-300 fluctuation. My mechanic said theirs air in the system and said it could be the head gasket.. has anyone came across this problem? Want to see if it could be something else before I pay for 20hrs of labor to replace it..

 

I would purge the air out of the system before committing to an expensive (and possibly unnecessary) head gasket repair. If the issue comes back after you purge the air, then you may have a big problem.

The factory service manual walks you through how to use the purge valve in the coolant system. I prefer using a Lisle spill free funnel with the front of the car slightly inclined. Using the funnel, the air should be purged after a few heat cycles.