I'd suggest:
1) switching to a diesel-spec oil right away.  I don't think there is
such a thing as diesel spec 20w50--I know, I looked hard when I first
got my diesel.  I run 15w40 which is widely available.  I use delvac
non-synthetic, fwiw.

Note: When I first got my diesel I ran it for maybe 7K miles on Castrol
GTX 20w50 (which is what I'd run in all my aircooleds), and then I spun
#3 rod bearing.  Coincidence?  Perhaps.  But now I don't want to take
the chance so I run only diesel spec oil with the proper additives to
deal with sooting and such.

2) Run a Bosch of Mann filter, if you aren't already.  If you are, try
a new filter.

3) Get a mechanic to use a mechanical oil pressure gauge to test your
oil pressure to see if you have a real problem, or if your sender is
just wacky.

4) If a problem is indicated, get an oil analysis done to see if /
where you have any excess wear on the engine.

I'm by no means an expert on this, but I have been through a low oil
pressure episode and subsequent main and connecting rod bearing
replacement.

T.

On Aug 10, 2004, at 2:16 AM, Alan Pickersgill wrote:

> I'm having trouble with the oil pressure light and buzzer coming on.
> I'm wondering if the collected wisdom of the list might know if this
> is because of over-sensitive oil pressure senders?
> Could it have anything to do with the type of oil filter being used? I
> remember debates about oil filters and pressure on vanagon engines.
> Does the wrong filter make pressure low or high?
> Any guidance would be appreciated.
>
> The background info -engine is a low mileage turbo diesel (140, 000
> km) with new 20W50 oil and filter and a brand new pump. Rod and main
> bearings have been inspected by a couple of experienced mechanics. No
> apparent damage despite 3 episodes of the light coming on.
> Light and buzzer comes on only when engine is hot (normal operating
> temperature) and after working fairly hard 3,500 -3,750RPM for five
> minutes or more. Then comes on when the RPM drops - coasting to a stop
> at an off-ramp. On another occasion came on when the rpm fell below
> 2,000 after cruing at 3,500 or more. Then when RPM went back above
> 2,000 it went out.
> I've installed a Hastings electronic oil pressure gauge and it agrees
> quite closely with the mechanics gauge.
> I get 29psi at 2,000 rpm and it goe up from there.
> Below 2,000 rpm it falls quite low 5psi at 1,000 rpm and even lower at
> idle 800rpm.
> Pressure at cold is 75psi or more.
> I don't think this should make any difference but this engine is out
> of a 93 Jetta turbo diesel and is now in a 93 passat turbo diesel.
>
>
> Alan
>