This sounds like a problem I once had with my '84.  Like yours, it
wouldn't show up until it had been driven for awhile and would go away
with just the slightest pressure on the brake pedal.

The noise appeared to be from a brake pad that was just barely dragging
against the rotor ... however ... In my case it was wheel bearing
related.  Maybe the bearing would get warm and cause a slight drag that
would cause the pad to rub.  Anyway, I replaced the wheel bearings and
the noise didn't come back.

If that hadn't cured it the next step would have been to rebuild or
replace the calipers.

Mike

Matthew Jenkins wrote:
> I have a 91 Vanagon GL Westfalia with about 95,000 miles on it.  Am having a
> problem where the front end starts emitting a high pitched squeaking /
> whistling sound after the vehicle has been driven about 20 minutes.
> Possibly from the driver side wheel well, but hard to be sure.  I was
> wondering if this falls under any well known "Vanagon syndromes" that I
> should look at first?  I had the brakes checked.  They are a bit worn but in
> decent shape, a bit of a groove that causes slight wobbling when one brakes,
> but plenty of life on the pads and not in need of replacing.  Problem only
> occurs after driving 20+ minutes.  Whistling goes away when I brake.
>