I just phoned the agent to enquire about this and here is the
answer.....

The older models had 3 pipes coming out of the coolant distribution
unit. The new ones (which my '89 Syncro has) have 4 pipes coming out of
it. The plug, clip and O ring are required to close of the 4th outlet on
the coolant distribution unit if you do not require this outlet.

Jimmy Sanby
Cape Town, SA
'89 Syncro 15"

>>> "Mark McCulley (Write Stuff)" <a-markmc@microsoft.com> 11/17 7:53 PM
>>>
 From the archives:
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The coolant distribution unit is a plastic piece that routes coolant
from
the engine to the radiator and rear heater core. For some reason the
syncro
uses a different part than regular vanagons (different hose routing
maybe?).Anyway, VW has made a change on this part you now have to order
a
plug to go along with it. Here are the relevant part numbers:
251 121 442 coolant distribution unit
357 121 140 plug
025 121 142 clip
N90316802 O ring

-Mark McCulley
87 syncro Westfalia