More likely would be that you simply have a bad cap on the tank. If your number ends in anything other than "-04", your cap has been superseded and needs to be replaced. Bad caps cause the condensation you describe, which seeps down and corrodes the bolt heads on the system bleeder valve assembly. Change the cap first, and then clean up the area, most likely the problem will not reoccur.
You are correct, the bolts thread into plastic, so be very careful about tightening them, they snap off easily.
Threaded Mode
