Notice that the 10mm bolts are not that big, don't tighten them too much or they can break off, and tapping them out is a real pain.
The replacement of the Air Pump and relay can be done from under the car as well as the way I am describing; I prefer going in from the top. You will be removing the battery from the car so make sure you have your radio code so you can get your radio working after you re-connect the battery. If you don't have the radio code, then stop by a Volvo dealer and they can get the code for you; for security reasons it is not given out over the phone. A 10mm wrench will allow you to disconnect the positive and negative cables from the battery. There is a plastic fastener that holds the battery in place on the bottom inboard side that fastens to the battery tray. Remove the fastener and slide the battery inboard and then lift it out of the car.
The battery tray is held in place with two 12mm bolts, remove them, and also a 10mm bolt that holds the positive cable in place to the tray. Once the bolts are out, slide the tray inboard to work it out of the fender. There are two rubber grommets that the tray slides into on the inboard fender. If they come out with the tray, take them off and put them back into the holes in the fender.
Once the tray is free of the fender, rotate it over so you can unplug the electrical connection to the cruise control vacuum pump as well as the vacuum line that attaches to the pump. Remove the tray and set it out of the way.
