I also say air pocket. I've found my ls3 to be extremely sensitive to air pockets and somewhat tough to bleed whenever I'm refilling the system.
Steps I take now:
1. Jack the front of the car up.
2. Fill the engine first through the upper radiator hose
3. Then fill the radiator
4. Remove the 1/4 steam by pass line and ensure a steady flow of fluid (bleeding out last bit of remaining air).
5. Run the car with the heater bypass open and allow the thermostat to cycle with the radiator cap off multiple times.
Throughout the engine running and subsequent first cool downs ensure that the radiator level doesn't drop below the upper hose outlet at the waterpump.
|