With out a shadow of a doubt, take it off and throw it in the bin! Fit a new O ring and blanking plate with the correct length of allen bolts.
I have seen the result of a broken one where the pin detached and scored the inside of the pump and it was ruined.
When it was circa -20 my 1hd ft didn't miss a beat, just more important to let the engine warm up before laboring it smashing snow drifts!