James,

Two possibilities:

1) Had a similar noise on my '87 a few years back. I finally found a nut loose
on the pivot bolt on the upper control arm - front suspension - on the
driver's side. Changing forces would tend to shift the arm fore&back slightly
on the loose pivot, making a slight thump just under the driver's seat - where
it's very hard to tell which direction it's from. Could also be worn bushings
or ball joints - but I'd suspect the front left suspension, as the noise under
the driver seems non-directional.

2) On my '91 had a small thump due to sticking brake shoes/cylinders on the
rear. Again, this sounded like a shift of something in transition from braking
to acceleration, but would often happen some seconds after releasing brakes,
when power was applied.

I rebuilt the rear brakes, since I had over 100K on them, but they were really
1/2 worn and had no obvious problems. I think the real problem may just have
been that I needed to change the brake fluid. The noise cleared up after the
brake work in any case.

Tom
Austin, TX
'87, '91, '97 (&'62 ragtop)

>----------
>From:  Vanagon mailing list on behalf of James Adams
>
>        I have a mysterious thumping sound on the underside of my van which
>happens about every 5 minutes or so when I am driving around town.<snip>
>
>        BTW, it is a 1990 Vanagon, 4 speed manual, 2.1L engine.
>
>        Any suggestions or guesses would be appreciated !  This list has been
>a very good source of Vanagon info, and I appreciate everyone's interest and
>responses in the past.
>
>
>Kind regards,
>James Adams