Hi Syncronauts,

Both diff locks refused to come on last weekend when needed, in the middle
of a grassy bog. No vacuum to dash switch. Took off the 3 balled vac tank
hung underneath, drained out the rusty/sandy/muddy water, it was half full!
Rinsed it out and let it dry while I checked the vac lines.  From the main
fat vac line (going up to brake booster) a T leads to the one-way valve that
lets vacuum build/stay in the reservoir. After valve, a Y connector leads to
dash switch via black plastic tubing and into the reservoir via a short
steel tube.

Tube was WELL rusted, sand/mud filled it end to end, and that leg of the Y
connector AND the one-way valve! Tube goes into vac res. via rubber collar,
put in collar then tube to expand/seal it all. It appears that this joint
had been leaking for a long long time, and enough deep water/mud had been
able to get in.

Fix was to chuck the steel tube, used a 3" bit of vac line from Audi door
locks (open the trunk, look for the lime green line and pull hard, gets two
4' lengths and a section of rubber splice). Rubber collar was cleaned well
and new plastic tube and collar gooped into place with ample sealing.

The one way valve tube just lets a WD-40 nozzle tube slip in with clearance.
5 minutes of blasting/shaking/tapping on the reservoir side of valve (the
one way feature had kept grit out of the other side) and it worked like a
charm again. Keep at it until easy to blow through and you can hear the
flapper moving/closing. It moves easily and doesn't leak when working
properly. Don't put it back in reversed! Rest of vac line fittings were nice
a tight/flexible, so I didn't goop them.

Some preventative maintenance for the aged Syncros out there, mine is 11
years old. HTH.

bye, Tim