Calling all Merc detectives:: Every once in a while my engine won't
shut off with the key, and the doors won't lock, so I know there is a
vacuum leak. Funny thing is, most of the time everything works quickly
and perfectly. The problem happens about one time in twenty. Doesn't
seem to have anything to do with air or engine temperature. So what
would cause such an intermittent problem? Does it give a clue as to
where the leak might be? What's the most efficient way to proceed when
tracking down the leak?