Thanks, I think my gaskets look ok for now; but I keep taking the manifold off and on trying to fix the crack. Mine is a bit more than a hairline; but I want hot tub.
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That's a serious crack. But honestly, do you have anything to lose by trying to epoxy it back together? It may be a temporary fix but might get you by till they are available.
Disassemble everything and pull out the valves. Clean everything thoroughly internally and externally with rubbing alcohol or mineral spirits. Drill a hole at the end of the crack to stop the spreading of the crack. Take a Dremel and bevel back the crack on the inside and outside. Sand with 120 grit a large area all the way around the crack on both the inside and outside. Reclean with rubbing alcohol or mineral spirits. Then put a small amount of epoxy into the entire length of the crack and put rubber bands or clamp the crack together. Clean up any excess and allow to drive for a couple of hours (~2+ hours).
Repeat the process over the cracks again and try to fill in some more of the cracks till flush on the inside. Cut pieces of fiberglass that extend about 0.5+ inches on either side of the crack and epoxy fiberglass over the exterior crack. Use a light coat of epoxy but enough to wet the fiberglass. Allow it to dry for a couple of hours.
Verify the interior crack is flush, if not add some more epoxy. Add more epoxy over the fiberglass and get a good strong coat. Allow it to dry for 24 hours now. Sand flush any mating surfaces so you get a good seal. After the cure period, spray paint with a satin black to make it look nice.
Then rebuild the heater (with it not plumbed in) and do a static pressure test. I would use alot of o-ring lube on all mating surfaces to ensure a good seal.
Parts I used when I rebuilt mine:
- Marine Epoxy (slow cure)
- Fiberglass Mat (way more than you need)
- Black Satin Spray paing
- Pressure gauge and schrader valve
Here are some photos of the pressure tester I built. I had to order the pressure gauge but I built the rest with random PVC I had laying around. The link above takes 3/4 NPT male fitting. Heck, I even thought about just encasing the Dang thing a block of epoxy since these manifolds are pure unobtanium.
Hope this helps. You got nothing to lose by trying to see if it works.