classic air pump sound...your motor is squealing because of poor Volvo design...Many many air pumps and check valves have been replaced on these models under the original warranty, and are now failing again in spite of fixing the original cause! This is just poor design. Late models no longer have these pumps. If your air pump motor seizes or draws too much amperage (and it may not until next winter), you will get a check engine light. Your car can't pass an emission test that way and you will be forced to have it repaired. But guess what? The air pump isn't covered under the extended emission warranty! This problem should be addressed by a Volvo recall. It is TOO WIDESPREAD.