In article <timmcn-E2F9A4.firstname.lastname@example.org>,
> I recently noticed that my 1990 240 makes a sort of sighing sound when I
> turn the car off. It seems to be coming from the dashboard and I wonder
> if it is not some part of the vacuum system controlling the vents. Is
> this normal or indicative of a problem?
There a vacuum hose from the manifold to the firewall that supplies
vacuum to the reservoir that sits on the floor under the center console
to power the push button vent switches. The nipple at the manifold is
too big for the hose, so there is a reducer that uses a small piece of
pipe to make a 90 degree fitting. The vacuum hose that fits over the
pipe splits and drops vacuum to the reservoir. When the motor is shut
off, you hear the air rushing in to fill the vacuum in the reservoir.
The goal when driving is to miss the maximum number of objects.