I removed my impeller bc of it was cracked. However I could not remove the shaft seal. It appeared to be stuck to the shaft. In fact it did not appear to be touching the back of the impeller at all (I.e it's stuck in a compressed position). I put the pump back together with the new impeller and left the old seal on. It does not appear to leak. Any ideas how to remove it? Or should I just not mess with it bc it's working.