OK so back 4 months ago I had a new radiator in the 2001 maxima and flushed the system all has been good since then, today I was checking all my fluids and noticed the coolant in the reservoir was fine so I opened the radiator cap and noticed there wasn't that much coolant,the coolant was barely up to the inside chrome frame maybe an inch or two down from the radiator neck, so is this normal or could something be happening?
Also I have lately been using my heater a lot, could coolant have gotten into the heater core lines to fill them up and keep everything flowing?

 

It should be full all the way. Very possible the air came from the heater core or there's a leak somewhere. Fill it all the way and check on it in a few days. That will determine if you have a problem or not

 

A bad radiator cap could be allowing the coolant into the overflow tank but not allowing it back in the radiator after the car cools off. If the cap is old, probably time for a new one.

 

Did you bleed properly the first time?