DrVanNostrand,Also repaired the coolant reservoir. It was cracked on top like so many of them. I liberally slathered JB Weld all over it. Seems to work well. Maybe I’ll leave it that way.
Unless you first cleaned the tank with denatured alcohol or better, I would be surprised if any epoxy would last long on the coolant catch tank. Even then, the flexing that cracked the tank would soon crack the epoxy. A wet layup of RTV and one layer of cotton cloth might last longer, and seal better.
No matter, really: the coolant catch tank is available new from the mothership, and it is cheap to buy.