A few years ago I replaced my coolant tank with a doorman or some other knockoff brand because the original one was cracked. Now a few years later the threads on the tank or cap have stripped and the tank doesn't seal. Fortunately it still runs fine and doesn't overheat, but its annoying to have to top it off every month or so. Ideally I'd like to devise another way to seal the system, but then I have to build in a pressure relief valve, and have some way to open it back up again. Anyone have any ideas on how to seal it back up, or am I stuck just buying an original tank and replacing the whole thing.