The problem with Bar's Leak is that it coats everything not only the leak.  It
coats the inside of the radiator and thereby lessens the ability of the rad to
shed heat.  How much more warm does a van with Bar's Leak in it run than a
normal van?  Could be only a few degrees or could be noticeable.  Also another
consideration is that BL is almost impossible to flush out of your system once
it is in there.
I like to use Moroso Ceramic Block sealer in my stuff 'cause it goes directly
to the leak, seals it tight, and you drain out the excess.  No fuss no muss.
And it lasts great too.
Thats my 2 cents
Ken Wilford
John 3:16