Date: Fri, 9 Feb 2001 19:54:13 -0500
Reply-To: 72510.1173@COMPUSERVE.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Helen Fahy <72510.1173@COMPUSERVE.COM>
Subject: Re: EXPERTISE NEEDED! oil pressure woes con't. part 4
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On my '87 Westy, with an oil cooler, experiencing the same low oil pressure,
~20psi, after climbing or at >65 mph, my oil temp ran up from ~210 to over
260 degf. Once it got that hot, I pulled over and stopped the engine.
After a worrystop, I started up the Westy and viola(musical instrument;) the
pressure got better. As I increased speed to >65, ~4k rpm the oil temp shot
up and the pressure dropped. Pulled over again, repeat. Note that the oil
temp did not drop if I simply reduced speed for awhile. Nor did the
pressure come up, obviously. Only stopping for awhile with the engine off
helped.
Hypothesis was that the oil foamed due to overfilling. I had the level
right at the upper fill level mark on the dipstick. This meant that the oil
got real hot as the oil foam to metal to water heat transfer is quite poor
for a oil foam. Raising the heat of the oil reduces the viscosity of the
oil and pressure that the pump is able to generate. I am measuring the oil
temp using a VDO oil drain plug replacement sender, so I should be at the
coolest point in the oil system.
Reducing the oil quantity in the sump & oil filter to 4 qts total, with std
Mahle filter, brought the temp back down to ~210 and the pressure up to
~38psi at 4000 rpm. I used a hand operated vacuum pump and sucked it out
through the filler. This ended up below the full mark on the dipstick,
about 1/3 way up from the low mark, ymmv. This testing was done on the same
road, same speed, same water temp,same direction and same temp, approx.
Through all the testing, the water temp gauge did not move from the 1 needle
width below the led. I have calibrated the sender with boiling water, so it
does work.
> Thanks for the info, and I would appreciate a response to the question of
> the oil pressure coming back up after being low. That really baffles me!
> Brian Cochran
> 84 westy
> Carnation WA
Letting the oil cool off and defoam will allow oils viscosity to return to a
damaged normal and the pump to develop full pressure.
The test is simple, reduce the oil level. Even at the bottom , the minimum
level , you will not hurt the engine. If the pressure vs operating
conditions stabilizes for a given rpm, then the fill level is the issue. If
not, then....
I have since switched over to the mahle diesel engine oil filter. It fits
and hold 10 oz more oil than the gas mahle filter. So now I precharge the
filter and add a total of 4 qts and 10 oz of oil.
The day before I change oil I add about 1/2 qt of Marvel mystery oil to the
crankcase. Thanks to Bob Donalds for that tip. I have not had a noisy
lifter since I started that regimen.
Joe Fahy
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