Since having my heater core replaced a couple of weeks ago, I've had a noise coming from (I think) the driver's side dash vent that sounds like a "marble in a pipe" or like a loose screw tumbling on fast turns. When my dealer replaced the core the tech put absorbent towels under the carpet to absorb the antifreeze (good) but then failed to remove them and reassembled everything with the towels in place (bad). I wondered why there were lumps under the carpet that I never noticed before!

So now I'm understandably reluctant to bring it back and allow them make something bad even worse.

I've tried probing the ducts to the rear seats with a magnet with no success. The noise sounds like it's coming from the driver's side dash vent, but I'm puzzled as to how something could have gotten dropped into that duct, which is higher than the heater core. I can see how it would be easy to drop something into the rear seat ducts, but like I said I can't find anything in these. Any ideas? I'd like to try probing the dash duct, my magnet won't pass between the vanes.

Brickboard archives say the SV70 vents pry out with a small screwdriver. Any tricks or cautions?

Going insane from the noise...

Thanks!

-Bob