Can flushing cooling system kill monovalve?
 

Just swapped in a new tranny and torque converter, finally putting the original to sleep after 245,000 miles. Car is shifting like new (actually better, considering the modifications made to the great rebuild I purchased from Ron at German Star!)

Anyway, I can't fully enjoy the ride yet, since I now have no heat in the cabin! The thermostat and water pump were working fine, so it had to be the monovalve. Sure enough, I removed it and the screen/filter was totally caked with debris and the rubber membrane was torn.

Now, I know these monovalves are notorious for failing (especially after 15-years of use,) and that it's a really easy and relatively inexpensive fix, but I don't buy that the timing of this failure was just coincidence...

QUESTION:
Can flushing the coolant (as was necessary before transplanting the transmission) foul and/or rupture these monovalves? And if so, would it be a wise precaution to remove the monovalve piston insert and plug the hole before flushing-away?