I had my 2006 Cadillac XLR at the dealer for a vacuum leak. The rubber coupling between the air intake and the plennum had to be replaced due to a split on the underside. The tech made the needed repair and put everything back together and then proceeded to start the car and expressed that he heard a weird sound. The car immediately shut off, he then proceeded to check his work by removing all the parts that were previously taken off. After reinstalling all that was removed, he again started the car and again heard a weird sound only now louder.

The lead/head technician thinks that something may have fallen into the heads while the plennum was off. They used a fiber optic camera to look into the heads to see what they could find, but found nothing other than two stuck valves. So at this moment my engine (4.6 Liter V8 Norstar) is being removed for futher investigation. The shop manager calculated that it will take 26 man hours to remove the engine and investigate what happened. All work will be covered under warranty and if the damage is significant they will replace the engine with a new one. I will not know until next week what damage was done.