The International Cessna^® 170 Association

Removed and cleaned my gascolator and after installing and purging any air, checking for leaks none noted.
I flew it for 30 minutes and checked the gascolator and seen about 1/2" of air in the top of it, after setting for 30 minutes I rechecked and no air was found in the gascolator.
Any thoughts?

The "air" is not necessarily ab-normal. The gascolator is slightly "uphill' from the fuel valve in the 3-point attitude. Any trapped air will stay there until the airplane attitude allows it to float uphill to the fuel tanks. If the air was there after landing, then it likely slipped out between the glass cylinder and the gasket. If the gasket doesn't leak gasoline, or leave gas stains, don't worry about it. (Air may excape where gasoline won't due to the gasket "swelling" after it becomes saturated.)