I have a Bissell Big Green 1672, the older canister model. Went crazy trying to figure out how to get to the pump. Finally figured it out. The top green "shell" covers the motor & pump and is separate from the "grey" plastic housing. Using a screw driver, insert it between the small gap between the top "shell" and the housing. If you look at it with it laying down on the top, you will see the small 1/4" gap. Gently pry in between the two and work your way around. It will start to lift up and then you can easily work your way around and it will pop off exposing the motor and pump. Note that the wires to the on/off & pump switches will sill be attached to the top shell. If you take them off note where they came from and make sure they are all on when you put the top back on. I have had my Green Machine for years, what a work horse! To bad they don't make them anymore, the new ones that replaced them just don't have the same durability and power as the older Green Machines.
Stephen
March 2009