Old Library

In a message dated 98-01-07 03:13:37 EST, you write:

<< >Yes, this is the auxillary water pump.  The VR6 is a low flow engine (for
 >emission's sake), requiring an extra electric water pump to circulate
coolant
 >through the heater core.  It is also designed to prevent boiling in the head
 >after shut down by continually circulating coolant.  It cycles with the rad
 >fan after run on OBD I, and for several minutes independently on OBD II.  It
 >has proven to be an early failure part and retails for around $170.  It is
 >controlled by the fan relay, which is the large black box with the 50A fuse
 >element that resides near the coolant resevoir.

 How early is "early failure" as applied to parts?  About when should I begin
 looking for the aux water pump to fail, and what are the symptoms?

 Best regards,

 Len "paranoia 'r us" Cleavelin >>


Hey Len,
The pump fails in one of two ways:  it begins to leak at the seals, or the
motor bearings begin to fail.  The leak reveals itself as coolant on the
trans, usually baking before it hits the ground.  The bearing failure reveals
itself as a noisy buzz when the pump is operating, progressively getting
worse.  I've had my own fail at around 50k miles, and customers' have failed
between that and 100k miles.  Most failures have been on Corrado SLCs, since
these have more average miles on them.  The replacement pump has a different
harness connector profile, requiring updating on the older VR6s, which may
imply a redesigned piece.
Besides the high shutdown cylinder head temps that may occur with a faulty
pump, there may be another side effect of blown heater cores.  Conventional
wisdom points otherwise, but actual experience makes me wonder.  The pump is
similar to a "fishtank" pump, in that the impeller is spun by means of
magnetic polarity.  There is no shaft that connects the impeller to the motor,
just a set of magnets on the impeller shaft, and a set on the motor shaft,
creating a magnetic opposition that spins the impeller as the motor spins.
This eliminates the possibilty of internal coolant leakage, yet it also makes
the impeller easier to spin when the electric motor is off (vs a mechanical
connection design).  Anyway, if the pump fails, the force of the coolant
should be enough to rotate the impeller and properly circulate when the engine
is running.  However, I had a customer with a dead pump, which resulted in a
cold coolant hose post pump, with the hose to it (from the heater core outlet)
being up to operating temp.  Coolant gauge read properly, yet there was
obviously a restriction in flow.  Many Corrado SLC owners suffer from blown
heater cores, many of which occur at relatively low mileage.  I'm beginning to
wonder if the failed electric pump may be a contributing factor.
It may be a good idea to check the pump operation periodically.  With then
engine running, is should be merrily humming away.  They can fail with no
noticable noises or leaks, too.

Regards,
Todd
Air & Water
VW Tuning
Philadelphia
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