Get a small can of Christy's red hot blue pvc glue at home depot, depending on how bad the crack is ( it sounds like a hairline crack ) then you can try, with the pump running ,and primed, to apply the glue around the crack and the suction from the pump will draw the glue into the crack, you should notice an improvement in pump sound, and visually through pump lid air should disappear, as it fills the crack, maybe get a large hose clamp to wrap around body and see if closes the crack after tightening clamp, i use glue sometimes on customer pools when i check for leaks on a jandy valve, or pump fittings,etc, if i notice air bubbles in pump basket area going away, i know i found a leak, the glue doesn't fuse to the plastic like a glued pipe joint does, plus i always re plumb areas that are leaking anyway so, if its just the ear where the screw hole is broken off, you can apply silicone instead to the area while it runs, goop it up around any place you think is not sealing, let it dry for a few minutes, then put some more on, put it around the edges of the cover plate, etc. since the damage is done, it really doesn't matter how you go about trying to save the valve, if the air leak can be stopped that's what counts,
Bear in mind , this only works on valves or fittings, that are on the suction/front side of pump that are leaking air, water/pressure leaks on the discharge side of the pump cannot be sealed this way " you cannot seal a pressure leak from the outside"