For suction, check that the filter hidden beneath the clear drum is clean, and next the fluted plastic pipe that connects the bottom sole plate (with the brush) to the motor area isn't off or split. Suction is usually excellent with the DC07 as far as the flexible wand goes, but less so with the machine upright. In fact, its best to press the sole plate in contact with the carpet with your foot. As for the dirt leak, is the bottom flap locking shut?
John
August 2009