Corbin Russwin door closers use hydraulic pressure to gently latch doors. After several years of use, you may need repair or adjust the door closer to keep it operating properly. The door might close too fast or too slow, slam, or be hard to backcheck while closing. The screws holding the unit to the door and the door frame sometimes work loose after several years of regular use. Repairing the closer is a relatively straightforward job with the right tools.
Stand on a stepladder to access the door closer while an assistant makes sure no one tries to use the door from the other side. Tighten each of the screws attaching the opener to the door frame and the arm to the door, using a screwdriver.
Check to make sure that the elbow screw -- the hinge point of the door opener's arm -- is tight. Add a little lubricant to the elbow screw and the joint where the arm attaches to the door. These parts tend to start squeaking after the factory lubricant wears away.
Remove the screw at each end of the door closer. Pull off the cover to reveal the hydraulic chamber and the adjustment screws. The closing speed valve is located on the underside of the unit, while the latch speed valve is on the end between the date and power labels.
Turn the closing speed Allen bolt clockwise to slow down the speed the door moves, or turn it counterclockwise to increase the speed. Spin the latch speed dial in the same way to adjust the final 2 to 5 inches that the door travels. Step down off the stepladder and test your adjustments.
Climb back on the stepladder. Adjust the backcheck bolt on the opposite end of the opener to the latch speed dial. Do not confuse the spring power adjustment bolt on the end of cylindrical part of the opener for this bolt. Turn the backcheck bolt clockwise to increase backcheck pressure; turn it counterclockwise for less pressure. Backcheck should provide a soft cushioning when the door is closing.