Date: Sun, 24 May 1998 01:56:45 EDT
Reply-To: SyncroHead <SyncroHead@AOL.COM>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: SyncroHead <SyncroHead@AOL.COM>
Subject: Re: Need some Oil Pressure help
Content-type: text/plain; charset=US-ASCII
In a message dated 98-05-23 12:05:53 EDT, KENWILFY@AOL.COM writes:
<snip>
> Anyway I just installed a 'wet' oil pressure gauge in my van
> and this is the first trip where I could monitor the oil pressure.
> It varied from 45 psi-32psi at 3000-4000 rpms after we were
> in the road for about 4 hours and the motor was nice and hot.
> Are these low readings?
It doesn't seem as if these are low by VW's standards. The switches they
installed to monitor oil pressure kick in at 0.3 bar for near idle engine
speeds and 0.9 bar for higher engine speeds. A "bar" (barometric) is equal to
14.7PSI. This conversion yields 4.4 PSI for the low speed switch and 13.2 for
the high speed switch. Appears as if your lowest hot, high speed pressure is
more than twice the minumum.
But (here's an important part) critical to any measurement is how you make
the measurement. In this case, WHERE you make the measurement is critical.
The oil pressure is highest coming right off the oil pump and it drops lower &
lower as it passes through restrictions (like the oil filter). Where are you
measuring your oil pressure, relative to where the VW's oil pressure sensors
are located in the oil's circuit?
> Why I asked was I was getting the oil pressure warning light and
> buzzer intermittantly. It didn't come on consistantly though.
> It might come on at 37 psi one time and another time it would come
> on at 45 psi. Sometimes it would only beep for a second and other
> times for 30 seconds (very annoying.
> I just changed the pressure sender a few months ago and since then
> I had no warnings until just a couple days before my trip. I had put in
> 30wt oil to see if that would stop the intermittant buzzer before and it
> didn't. Then I changed the sender and that seemed to fix it. Then last
> week I was driving on a hot day and after about an hour at highway
> speeds it started again. I changed the oil to 20w/50 and put on a new
> Mahle filter. I checked the pressure relief piston and spring. The spring
> seemed springy and I cleaned the piston area out with some break
> cleaner. So now you know what I have done already. If I am having a
> low oil pressure problem I wonder if the motor is getting too hot? The
> needle stays in the middle or just below it so it doesn't seem like it, but
> I don't have a oil temp guage so I really don't know.
> So what should I do? Change the sender again? Check the wiring?
> Change the thermostat to a cooler one?
The dynamic oil pressure monitoring system gets inputs from two pressure
switches. One switch is closed with no oil pressure and opens when oil
pressure rises to about 0.3 bar, called the 0.3 bar switch. The 0.3 bar
switch is located between the left (driver's side) two cylinders.
The other switch is open with no oil pressure and closes when oil pressure
rises to about 0.9 bar, thus called the 0.9 bar switch. The 0.9 bar switch is
located below the water pump & crank pulley, near the oil pump.
If you're mesuring at one of VW's oil switch locations, I'd begin by checking
the wiring & "Dynamic Oil Pressure Monitoring System". Rig up a light
directly to VW's oil pressure switches to see if one is really switching. The
0.9 bar switch will make the light come on under normal pressure and turn it
off if pressure is too low. The 0.3 bar switch will turn on the light when
pressure is too low. If the test lights do not indicate low oil pressure,
then it's in your wiring or electronics. If the test lights show that the
switches are engaging, you either have a faulty switch or genuinely low oil
pressure.
Good luck,
Jim Davis