I agree with Jim.....sounds like a fan problem
Had a very similar problem myself recently with my 90 water-cooled Carat.

My VW mechanic (Ken Nethkin in Fishersville, VA) replaced the sending unit
and it seemed to fix the problem initially (I could hear the fan come on).
However I was still unhappy with the temperature the van would run in
traffic so he actually replaced the thermostat in the engine....seems that
by default it was rated to keep the coolant in the engine till it reached
190 deg.  So he swapped it out for a unit rated to 180 deg (kept the old one
to switch out if needs be during the winter).  He also put a manual switch
in so I could engage the fan manually if I was getting a bit anxious in
traffic).

Ken Wilford has a quick and easy way to trouble shoot the radiator fan
system at
http://www.vanagain.com/How2fan.htm

Best luck to your friends
Joe Chasse
90 Carat, Charlottesville VA

----- Original Message -----
From: "Jim Henry" <jch@JCHGIS.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, July 16, 2003 9:55 AM
Subject: Re: 2.1L coolant light problem

> This sure sounds exactly like the fans are not working.
>
> jim
> Durham, NC
> 84 westy
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
> Of Vanagon Man
> Sent: Monday, July 14, 2003 4:29 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: 2.1L coolant light problem
>
>
> This is on a neighbor's van............
>
> They have a vw reman engine in their van that was installed about 2 years
> ago, Maybe 30k miles on the motor.  They say that the car runs great, but
if
> they get stuck in traffic somewhere, the coolant gauge needle climbs
almost
> to the top, and the red light starts flashing............once they get
> moving again, things get back to normal.  He says that he does need to add
> coolant periodically to the car.  Also, claims it does not leak from the
> heads, or anywhere else he can see.
>
> They recently took it to a shaky vw shop, where they bled the system, and
> pressure tested it, and all was supposed to be well.....the mechanic told
> him that the system was "air-locked" and needed bled.  Well, the problem
is
> still occurring, they love the van, and soon have to make the 4500 mile
> drive to Seattle to relocate.
>
> I told him that the first thing i need to check for is exhaust gas in the
> coolant.  If indeed it is present, he needs a head resealing........I
cannot
> think of any other tests to try to stop this for him, other than to be
sure
> the radiator fan is working.............
> .
> Adam P
> 81  Westy "The Brick "
> 70 Single Cab "Whitey"
> 74 Beetle "Ol Yeller"
> 73 Transporter (STILL at paint shop)
> 1988 Vanagon Wolfsburg
> 1976 Transporter (New CA bus)
> 1974 412 "Goldmember"
> Used Vanagon Parts for sale (mostly aircooled)