This issue has shown up in the archives, and my '85 has experienced this,
too.  In my case the problem turned out to be a loose radius rod nut(strut
bar) where it goes through the frame. Each time the brakes were used, the
front end would dip a bit, and the rod would rub against the metal frame.
What was originally a 3/4 inch hole for the bar to stick through became
about 1 1/2 inches. The bar would bang and bang on the frame each time the
brakes were applied. The reason for the loosened nut was that the large
rubber donut like bushings had disintegrated, leaving lots of space there.
Finally, one of two bolts that attach the strut bar to the lower control
arm, snapped. Getting interesting now! That was when the PO sold the
Vanagon, and I received my sentence, or part of it.

The fix was to get a welder to fill in the large hole and make it
smaller-$75. A shop had to press out the broken bolt. Vanagon then needed to
be realigned.

Shortly after that I just rebuilt the entire front end. I figured that all
the parts were going to be in similar condition. 150K