1972 Swinger front disc brake master cylinder cap seal

If you have a leak around the gasket and it is a newer parts store MC, then the problem is likely in the cap. They look to be softer steel and can distort more easily, and the stamping is such that it does not put even pressure on the gasket. We just fixed ours (I think); I'll post in a new thread when it is sure that it worked.

If you could get a NOS gasket, that may be good too; I suspect the new ones today have the wrong hardness and are not as compliant as the originals.