o I've recently taken these things on as a hobby, lol. Always loved a good challenge, and these are good for that. So anyway, I like to snap phone pics of a project sometimes, and this time I decided to put them to use. So.... Welcome to class.
Air pump motor repair 101:
1.) Loosen the 3 PH00 screws and remove the pump as an assembly.
2.) Remove the 2 PH1 screws that hold the pump housing in place. Remove the pump housing and metal bracket plate. Pull the plastic eccentric hub off the motor shaft Now you have a bare motor.
3.) Bend the 4 crimps outwards. You can then gently tap the motor shaft on a hard surface until the back cover of the motor pops out. If it doesn't pop out easily you probably have a crimp or two that need to be bent out further. NEVER pull on the terminals, you will ruin the brushes. It is advisable to attempt to remove the armature with the brush holder (back cover) as an assembly. If you can't, its ok, but the white plastic thrust washer will need to pull past the brushes since its stuck on the shaft, so be VERY gentle, the brushes bend easily (and *do not* bend back easily).
4.) Gently remove the armature from the back cover, and remove the white plastic thrust washer. You can then clean up the armature and commutator with some fine (like 320 or so) sandpaper. Do not put the white plastic thrust washer back on the shaft just yet.
5.). Now you need to make a tiny round-file. I used an 1/3 unbent paperclip, and roughed up the long end with a dremel tool cutting wheel. Use this "roughed-up paperclip" to file the rust out of the front bushing, and blow clean. Clean any rust off the magnet inside the field casing. I like to apply a thin film of oil (I've been using 3-in-1) to the armature, commutator, and magnet. Make sure to oil the bushing you've just cleaned too, and run the long end of the shaft in/out and spin it in the bushing to distribute the oil.
6.) Gently close up the brush gap to allow almost no space between the brushes, this allows the brushes to hug the commutator tighter. Drop some oil into the back bushing (inside the rear cover/brush holder). Use the oil to stick the white plastic thrust washer over top the bushing hole, behind the brushes.
7.) Now gently use the armature shaft to push and wiggle the brushes out of the way (again, *gently*!)to get the commutator past them, and slide the shaft thru the thrust washer, into the bushing. Now you have the armature/back cover as an assembly again.
8.) Now its time to slide this assembly into the field casing. Make sure to line up the keyway first. The insertion must be done in one smooth movement, as to prevent the magnet from "sucking" the armature into the casing, and pulling it back out of the brushes. If this happens, you must repeat the latter half of step 6 and all of step 7. I try to cock the armature in the housing and "scrape" it into place, then this way it has friction as it rubs down into place.
9.) There is a little step shelf inside the back of the casing that prevents the cover from going in too far, so once its in place I use the tip of my PH1 screwdriver to tap the cover down. Now you can re-crimp the 4 points and test 'er out.
You should have a "like-new" pump motor when done, provided yours was not totally rusted out in the first place. I have found that the main failure point is the front bushing (where the water lays when it drips into the back of the motor) and filing and oiling the bushing seems to do the trick.
And remember, if you don't fix the leak, or umbrella the pump, the same problem will repeat. Have a look at my post about FWD solenoid valve removal, this will stop the leak, but the procedure is still in beta testing.