Constant Clunking

OK, I have had this happen and it is as frustrating as trying to talk to a health insurance rep denying coverage for a medication you have taken for many years.

I will save the long story. I had replaced the A/C compressor and placed the core in the box in the trunk. Duh! Everytime I gave her gas, thunk. Everytime I hit the brakes, thunk. Everytime I turned a corner ka-thunk-thunk-ka. It was almost 45 days before I returned the core. On the way home, no more thunk.