The sealer probally dried and cracked.Thats why I always install my pan dry.Ive run them like that for 40 years and never had any leaks.I even run aluminum intake steel heads and aluminum heads and intake that way.As long as the heads and intake are clean and flat they seal.Back in the 60s we reused the pans all the time.They were expensive then at like 25 bucks a pop.Just some silicone at the 4 corners and under the hold downs.Rocky