If your pump is leaking where the motor meets the plastic pump housing, it is most likely the pump seal that needs to be replaced. Luckily, replacing your pump seal is a fairly simple process, provided you follow these simple steps.
Remove the pump impeller cover. Next remove the impeller. The impeller is threaded onto the motor shaft. Depending on which brand motor your pump has you will use pliers or a flat head screwdriver to hold the shaft still while you unscrew the impeller.
The pump seal is a 2 part seal. You MUST replace both halves of the pump seal. One part will come off with the impeller. Look at how it is assembled, the new seal will go back the same way.
Remove the seal plate from the motor to gain access to the second half of the pump seal. Usually there will be 4 bolts that hold the seal plate to the motor. Inside the center of the seal plate is the ceramic part of the pump seal. Be careful not to damage the plastic of the seal plate. You can push the seal out from behind by using a screwdriver to knock out the old ceramic seal. Note: Be sure the rubber ring seat is removed with the ceramic portion.
Clean the motor shaft and the seal plate. Inspect the seal plate for damage, cracks, melted or out of round which will cause the pump to leak even with a new seal. Carefully inspect the impeller for cracks or breaks.
Never touch the white ceramic face of the new seal with anything metallic or greasy. The new seal must be clean and scratch free. Press the ceramic part of the seal into the seal plate with the rubber part towards the seal plate and the white ceramic facing away from the motor. Do not lubricate the seal with anything besides water. Reinstall the seal plate onto the motor. Slide the spring seal part over the motor shaft. Push it past the threads. The black carbon face of the spring half of the seal needs to make contact with the white ceramic side.
Replace the impeller by holding the motor shaft and threading the impeller onto the shaft hand tight only Replace the impeller cover and spin the motor shaft to make sure the impeller does not come in contact with the cover or the housing.
Inspect and lube the pump basket housing o-ring. Assemble the motor and pump basket housing. Be sure and prime the pump with water before turning on the pump. A pump that runs dry can damage the seal and cause it to leak prematurely.