> At 11:37 AM 6/19/2001, pensioner wrote:
> >Odd.  I always thought the valve was closed at below 20PSI, routing the oil
> >away from the filter at low pressures, rather than the reverse of bypassing
> >the filter at high pressures/volumes.
> >
> >pensioner (one more day pumping air and getting more confused)
>
> Hmm.  Lessee.  There are three valves I know of, two in the filter and one
> in the motor.  The one in the motor limits maximum system pressure -- it
> only operates when the oil is cold.  Some folks seem to have the idea that
> setting that one higher will improve hot pressure, but they're doomed to
> disappointment, unless it's defective.   In the filter, one bypasses the
> filter element when it gets clogged (and thus causes too much pressure
> drop)

When it gets clogged and also when, such as with a cold engine, the
filter is an excessive hinderance to oil passage.  At that point only
part of the oil is filtered on each go-round and the other part passes
through the bypass valve instead of the element and travels straight
down the center and out.
-Dana-

> and the other is a check valve that keeps oil from draining back down
> out of the galleries when the motor stops.  This last one is the one that's
> missing from most non-OEM filters, which leads to lifter noise on starting.
>
> d
>
> David Beierl - Providence, RI
>   http://pws.prserv.net/synergy/Vanagon/
> '84 Westy "Dutiful Passage"
> '85 GL "Poor Relation"