A friend's late-model Blazer with Vortec 4.3 engine has been getting what she describes as "vapor lock" on hot days. Not all hot days, of course -- in particular, my all too brief and infrequent chances to look at it seem to reduce its temperature considerably.
The main symptom is, apparently, troublesome hot restarts.
Apparently she consulted a mechanic who threw up his hands and told her, "Those are known for that." Well, my theory is that there is likely some specific mechanical fault when a modern car exhibits those symptoms, and tracking down spooky intermittent problems in that cramped space under especially selected hot conditions is maybe just not his favorite pastime. But I thought I should see what the collective minds of rec.autos.tech thought of the problem before diving in.
--Joe