I second the Bar's Leak idea. It works. If you don't get all the coolant
out, though, it turns to green jello, and you have a big problem on your
hands. I've seen pics on the Saab website.

One other suggestion would be to use "normal" Bar's Leaks on it (not HG
Repair) and then if that doesn't help, flush completely and use the Head
Gasket repair stuff.

A phone rep at BL told me you could actually have something like a 10%
coolant solution left in the system, but I wouldn't want to risk it.