PS PUmp rebuild?
pjrose at frontiernet.net
Mon May 9 16:46:42 EDT 2005
At 11:28 AM -0700 5/9/05, Bernie Benz wrote:
>No! Is best to isolate the leak to a specific cylinder head before pulling
>the pump, as you may not have to pull the pump
> or at least will know just
>which one needs to be opened and the O-ring replaced.
Bad advice! Once it's decided you need to remove the pump to replace
one, yopu ought to replace _all_ those cylinder-cap o-rings. If
you're in the midst of a pit-stop and thus a few minutes extra time
is critical, then perhaps just replace the one that leaks--but
ordinarily it's a penny-wise pound-foolish way to go. These o-rings
most likely share a common "history"--meaning age and/or poor
technique during installation. There's no reason to expect that the
other o-rings are not near the failure point.
>These O-rings don't
>wear out, just fail because of poor installation.
That's not necessarily fact--just your considered opinion. My opinion
is: O-rings, like any synthetic polymer material, are subject to
age-related embrittlement (this derives from the inevitable changes
due to a phenomenon called "free-volume relaxation"-- sometimes
called "enthalpy relaxation"); and that changes the rubber's modulus
and its ability to recover from compressive deformation. Couple that
with constant thermal expansion/contraction and the material can have
poorer and poorer sealing ability over time. This scenario doesn't
even account for possible effects from contact with the hydraulic
>I agree with Bernie that there can easily be damage (from excessive
>stretching) caused by inadequate lubrication during installation.
>But if one of those 8 o-rings suffers from poor installation, what
>are the chances for the other seven?
mailto:pjrose at frontiernet.net
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