Date: Wed, 7 Jan 2004 23:41:47 -0800
Reply-To: Ben S <phlogiston@ISPWEST.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Ben S <phlogiston@ISPWEST.COM>
Subject: what causes low oil pressure
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well recent events (see my "blown head gasket?" thread) and the "oil
light discovery" thread have gotten me thinking about oil pressure.
to recap what happened to me: i have put over 20k miles on my van in the
last 4 months, and many of those miles involved strenuous hill climbing.
recently, i moved up to south lake tahoe and decided to switch to a
lower viscocity oil because of the colder weather. i did the oil change
down in davis where it's warm and was driving back up the mountain that
night when my oil pressure light came on. i stopped and ended up
getting the van towed. after i mistakenly diagnosed my problem and was
corrected by you guys, i drained out the 10w-40 that i had just tried
for the first time and replaced it with 20w-50, which is what i had
always used in the past with no problems. since that change, i have
driven over a few passes with no issues; but yesterday on my way up to
kirkwood, as i was climbing a particularly steep hill (meaning i was in
3rd gear at about 4k rpm for several minutes), the oil pressure light
came on again! so i let off the gas and the light went off. after a
few seconds, i tried to speed up again, and again the light came on. so
i slowed way down and cruised up the rest of the hill really slowly in
second gear and didn't see the light again. now for the record, i have
a fram gold oil filter in there right now, and i have heard all the
stories about non-german filters causing problems. however, just before
my recent oil change, i made several trips over these exact same
mountain passes, driving just as hard, with castrol 20w-50 oil, and
never had a problem AND i was using a napa filter then, too.
so although i know that i need to start using a real german filter (i
just ordered a 4pack from cafe volks), i think there might be some sort
of slowly deteriorating condition here--it seems like some subtle
problem must be getting worse. what causes the oil pressure to get low
enough to trigger the light? assuming that the oil was getting too hot
and thin from all the climbing, why did the pressure go up so quickly
when i let off the gas? the oil certainly can't cool down that quickly,
and i would expect that a decrease in engine speed would decrease the
oil pressure. and wouldn't my coolant temp gauge have registered some
kind of increase if the oil was getting too hot to maintain pressure?
but that temp guage was pegged right in the middle like it always is
once the engine warms up. i don't think this problem is caused by a low
oil level--i've been keeping a close eye on that. but could it be
caused by a fault in the pick-up tube? or a failing oil pump? what can
slowly degenerate and cause the oil pressure to drop under a hard load?
has anyone else had problems running 10w-40 oil? my manual says that
is safe for up to something like 75 deg F ambient temp, and it sure was
a lot colder than that when i had this problem.
thanks in advance for any help...
Ben.
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