There's no good way to fix it. Is it under warranty?
Even if it's not under warranty, Jandy might replace it for you if you ask.
That type of plastic does not hold adhesives well. Also, a crack in a pressurized vessel creates a weakness that could allow a complete failure. I would recommend replacement.
To get it to separate, you have to remove the impeller and then the four screws the hold the motor to the seal plate (backplate).
However, based on the age of the pump, it might be better to get a whole new pump that would be more efficient.
Ok, after you remove the six screws from the pump's seal plate you will need to pull the motor AND the drivetrain. It will look like this: http://wetheadmedia.com/wp-content/...gging-Impeller-On-The-Hayward-Super-Pump-.jpg
The the cone at the end of the motor will be the diffuser, remove the two connecting screws: http://www.mypoolyard.com/images/products/jandy_php_wftr_mhpm_jep_shp_pump_diffuser_r0445400.jpg
Then you must remove the impeller which is a little complicated but can be see here: https://www.youtube.com/watch?v=C41Rp4bkNK4
Yes, I get that, but when I take the 6 screws out, the whole assemble is pulling back maybe 1/4 inch and no further.
There are 8 screws, not just 6. There are two at the bottom that need to come out.