Hi,

I've had same probs.  I think it is due to water sitting in the area right
behind the tail light. The 'snorkel' that Syncros have runs right up to the
plastic grill, but VW didn't make it absolutely waterproof up top, so they
'fixed' it by drilling a small drain hole at the very bottom most piece,
and elbow.  This drain hole rests on the tin floor behind the light, and
any water standing in  there is nicely sucked up.  Typical VW design
effort...  do a half-assed job, then add a half-assed bandaid.

Take out the tail light and housing an you get easy access.  Clean the
silt/mud/leaves out and wedge a 1/2" thick bit of wood to keep the elbow
off the floor. Clear any drain holes in the tin. Might check the relays in
there for crud while you are at it.  And submerging your Syncro to that
depth when fording is pushing it, the block of wood won't help you then
either ;).  bye, Tim