Just had a discussion about sealants last week with a very experienced
mechanic whose opinion I respect very highly.
The only 'safe' products in his opinion are Silver Seal, Aluma Seal, or
a product that comes as a silver colored pellet (name unknown).  All
others come highly NOT recommended, problems plugging radiators, etc.
AND even those that work are a temporary fix.
BTW, I've used BarsLeak in the past and my recollection is that it
didn't solve my problem (not a VW engine).