The 40mm is the older style and the 30mm is the newer used since about 1981
or so... the pumps are fully interchangeable, just that you will need the
correct pulley to match the hub.

David Marshall

Fast Forward Automotive Inc.
4356 Quesnel Hixon Road
Quesnel BC Canada  V2J 6Z3
mailto:info@fastforward.ca <mailto:info@fastforward.ca>
http://www.fastforward.ca <http://www.fastforward.ca>
Phone: (250) 992 7775           FAX: (250) 992 1160

� Vanagon Accessories and Engine Conversions
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-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of Maynard Southard
Sent: October 28, 2001 10:21 AM
To: vanagon@GERRY.VANAGON.COM
Subject: 30mm vs. 40mm Hub on Diesel Water Pump

Brace yourself for a dumb question ... Can anyone tell me what the
difference
is between the 30mm and 40mm hub on the water pump for the 1.6L NA diesel?
(Please don't say 10mm!)

The Vanagon diesel requires a 40mm hub on the water pump.  I've always
thought
the dimension referred to the diameter of the surface that the pulley
attaches
to (the "hub", right?), but I have 3 water pumps on my work bench, one from
my
'82 Westy diesel (and I know it is not original), one from my '82 Passenger
diesel (and I know the whole engine is not original) and one from an '84
Jetta
Diesel with no A/C (which supposedly also takes the 40mm hub, but I know it
is
not original also.)  The "hubs" are all the same diameter, but the vanes are
different.  One has formed steel vanes (kind of like bent fork tines) and
the
other two have a cast vanes (and they are not identical).  Am I just looking
at
different manufacturing approaches to the tines, or have I misunderstood
which
hub the measure refers to?

And finally, why does VW use two different hub sizes?  I think it has
something
to do with the pulley drive system - as the Vanagon application uses one
belt
to drive the water pump from the crankshaft pulley and a second belt to
drive
the alternator from the water pump pulley.  On late 70's and early 80's
diesels
with A/C, there is a single belt that drives the water pump and A/C
compressor
from the crankshaft pulley and another belt that drives the alternator off
of
the A/C pulley.  These all seem to spec the 30mm hub.  Is the difference
because of the way the pulley is attached?

Thanks for any insight.

Maynard Southard  (OvO) '79
'82 Westy Diesel "Reinhardt"
'82 Vanagon GL Diesel "Sluggo"
'93 EV GL "Klinger"
'00 Golf GLS TDI "WooHoo"
'84 Jetta GL TD "Donor"