Sounds like you have air in the system since you replaced the elbows. Do this.
1. Remove thermostat housing from top of engine.
2. Fill with coolant.
3. Squeeze lower radiator hose to force air from the system.
4. Top of again
5. Reinstall Housing
6. Open up radiator cap.
7. Fill with coolant
8. Squeeze upper radiator hose to get air out.
9. Fill with coolant
10.Replace Cap
11. Fill overflow
12. Start car with heat on for about 15 min and let it come up to temp
13. Shut it off, let it cool and then top of reservoir.
