Man, I used to roll my eyes at guys who made a big deal about wetting forms, figured it was just something old timers nagged about. Then I watched a pour crust up on me the same way and now I'm the guy walking the forms with a hose myself before anybody touches a chute.

Wanna try this too, sounds like a blast.

Did you check the contact points inside the new cap? I've had repops where the brass was paper thin and the spring tension on the center button was weak right out of the box. That hairline crack you found is usually a sign the plastic got cooked or it was dropped before it ever hit the shelf. The old Motorcraft caps had thicker Bakelite and real brass, not this cheap pot metal stuff they pour now. Heat cycles under the hood will split a bad cap in a month, easy. Grab a NOS one off eBay if you can, those things last forever.