I have a heatilator eco wins18 and i was wanted to remove one of the washers so i could get a tighter seal so i took the lock nut off and i see theres a keyway and a key. I tried prying a bit with various screw drivers and it wont budge. Do i need a puller for this? I was going to heat it with a torch but im afraid that uneven heat on the glass might crack it.