That seal is not foam, it is a neoprene seal. Anyway, a product like 303 protectant should revive it some.
I would fill that crack/joint, and all others, with black silicone windshield sealant to eliminate the source of water intrusion.
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2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member,FMCA. "We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert the Constitution." Abraham Lincoln
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