My 2006 Prius, 102000 miles, has developed a loud noise that may be occur every 2 or 3 minutes or maybe not until 30 minutes has passed. At first I thought a tire was coming apart an impacting the wheel well but tires are all OK. Hard to tell where noise originates but it is loud like a bowling ball is rolling around in back end of car. HELP!
It might help if you could describe the noise. "Bowling ball" sounds like a banging, can you confirm that it's not a grinding or clunking sound? Is it just one "bang" or is it several? I'd suggest bringing a passenger who can try to localize the sound as you drive. If it happened to me one of the things I'd check is to make sure all the lug nuts on the wheels were tight, and also check inside the wheel wells to make sure there aren't any foreign objects lodged in there somewhere.
The emissions charcoal canister hangs under the rear of the car between the rear wheels. It's pretty unprotected, and could have been jarred loose. Check under the back of the car and make sure it's secure. EDIT: Just saw your car is a 2006 Prius? Not a Prius C? Still worth a look, but I'm not sure about the canister location on the gen 2.
