First, you are not an idiot, at least in regard to this job.
Regarding your previous post about cleaning the mating surfaces:
It sounds like someone else has applied a fully hardening cement to the gasket, where they should have either applied none at all, or a non hardening type.
Let's hope you have not made the same mistake.
Applying it both surfaces will do no harm, except making it a bit harder for the next guy to clean up.
Cheers
Regarding your previous post about cleaning the mating surfaces:
It sounds like someone else has applied a fully hardening cement to the gasket, where they should have either applied none at all, or a non hardening type.
Let's hope you have not made the same mistake.
Applying it both surfaces will do no harm, except making it a bit harder for the next guy to clean up.
Cheers
