Hi Colin,
I agree with David Most.  It's most likely your rear heater core
leaking.  I've replaced two. One on my former '85 and one on my '90
Westy (same symptoms drip out by sliding door floor).  On my wife's '88
the previous owner had the rear heater removed so I installed a new unit
and heater core.  Check out your rear heater and if you give me a call
I've got a new heater core and I could help you put it in tomorrow
(Thursday).  My labor is cheap for a fellow listmember(beer)...give me a
call at 408-244-5143.  I'm in Santa Clara right next to San Jose.

Russ

Colin Carmichael wrote:
>
> I drove my 91 GL from Oklahoma to my Dad's house in
> California last week.  Didn't have any trouble at all
> on the trip out.  However, I noticed a leak after
> driving the van this afternoon.  It's dripping on the
> far right side of the van underneath the sliding
> passenger door.  I assume a coolant hose needs to be
> replaced (? - I'm not a mechanic).  The coolant was
> about a pint low when I checked it.