Clunk noise from motor and heater issues. What's up?

Hi guys,



I'm having issues with my heater along with a cold start engine clunking. First off, I have an '03 325i. I recently filled the coolant since the previous owner was running the car empty. Now when I accelerate the temperature gauge goes to blue and the heater blows cold air. On the other hand, when I'm sitting at a light or idling in the driveway the gauge moves to normal(middle) and the heater blows warm air. I figured I botched the coolant refill procedure and air was trapped in the system. So this morning I went through the procedure again. After finishing the refill, I started the car and now I hear a loud clunking noise coming from the intake manifold area. Sounds like a golf ball inside a coffee can. I pressed the gas pedal and the noise didn't change at all. I checked the dash and there are no error lights on. I even put the cheap scanner on, no codes. I turned the car off and started again but the noise came back. I let the car run until warm and now the noise goes away. I am at a loss! Any suggestions would be greatly appreciated. Thanks in advance!!!