I used blue devil head gasket sealer and so far have a good result. I am currently driving the vehicle with just water and the sealer in system. It's running cool and it's not using any water. My question is, does the sealer continue working or is it only active for the first 50 minute idle procedure (i know it is attracted to the hot spot in the system)? Does the sealer become inactive after it's a initial use?
I've never used it so don't know, but would assume it will continue to work after the fact. The thing I'd look at if I were you is actually getting the water out of there and putting coolant back in. When you do, I'd highly suggest you put another bottle of the sealer back in with it.