Trump:

Once, I had a car (not a MB) that had a problem that manifest itself before warranty expiration. The dealer did a poor fix, that fixed nothing. When I got back with the dealer about this, my car was out of warranty, so guess what their excuse was? Well, I had the work done, and then sued the dealer and the manufacturer on the grounds that I had reported the defect before warranty expiration and the dealer had failed to correct. Guess what? I won what I paid for the fix, plus some consequential damages and attorney's fees.

IMO, if you report the problem to the dealer during warranty, allow the car to be examined, and the problem is not fixed but turns up again shortly after warranty expiration, I think a court would find you are still covered.

Hope this helps,
Richard