19 How do I know whether my water pump is going bad?
Description
This article is from the VW Technical FAQ, by with numerous contributions by Jan Vandenbrande others.
19 How do I know whether my water pump is going bad?
A: Obviously if it starts to leak either through the pump half seam or the bearing (the little hole on the bottom).
However, there are also other failure modes you have to be aware of:
If the car makes a grinding whish-whish-whish sound when cold <NOISE> which
diminishes as you drive, the pump bearing may be failing and the impeller
is machining the pump housing into slivers.
To check for this condition, remove all belts, and spin the waterpump
pulley. If it turns well damped and smooth, it's fine. If it feels gritty
and crunchy, it's machining itself. If on the other hand it spins loosely,
the impeller may have detached itself from the shaft.
Note that you should not mistake the grinding whish-whish-whish <NOISE>
sound from a regular whish-whish-whish noise. <NOISE>
In this case the belts may be simply getting hard or the pulleys are out of
line.
To check for this, take a can of Silicon spray and spray it on the belts
while the car is idling. If the sound disappears immediately, you found the
problem.
Either replace the belts, or use some hard soap on them (but don't lose
your fingers for this either).
If the pulleys do not line up, check whether any of the bushing are worn
(e.g., the rubber alternator bushing as found on older A1 VWs is notorious
for wearing out). Otherwise use spacers and O-rings to get them to line up.
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