Thank you for this helpful reply. Based on this I removed the excess oil.
So far the warning light and buzzer have not returned. Fingers crossed that
was the culprit.

On Monday, May 4, 2015, Dennis Haynes <d23haynes57@hotmail.com> wrote:

> Part of your problem maybe that it is slightly over the "Full" mark. That
> is not the "Full" mark. It should be labeled what it really is. It is
> "Maximum" do not ever exceed no matter what mark.  Seriously, the water
> boxer can be very sensitive to oil level in addition to viscosity. When
> overfilled the crank and cam will churn in it causing it to get hot and
> possibly even aerated. Both will reduce oil pressure. In addition the
> excess will get carried past the piston rings (pistons on their sides) and
> get carried out where it can foul the o2 sensor and the catalytic
> converter. This happens over time during extended high speed-load
> operation.  And what oil viscosity are you using?
>
> Check the archives for more information. Basically there are two oil
> pressure switches. The higher pressure switch is looked at when the engine
> is over 2,000 rpm. That will give the light and buzzer. Once on it will
> stay on until the oil pressure becomes adequate or you cycle the ignition
> switch. If you have the correct .8 bar sensor it is telling you that you
> didn’t have 11-12 psi oil pressure over the 2,000 rpm.
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com
> <javascript:;>] On Behalf Of Kk Al
> Sent: Monday, May 4, 2015 5:34 PM
> To: vanagon@GERRY.VANAGON.COM <javascript:;>
> Subject: That oil buzzer
>
> 87 Syncro here
> We are on long weekend. It's a nice 76 degrees out. Van is running well,
> temp is normal. Fresh oil and filter. When we pull off an exit the oil
> buzzer goes off and warning light turn on. We stop, check the oil. It's
> slightly over the full mark and clean.
>
> I thought I read somewhere that the oil light can come on due to high or
> low pressure.
>
> Thoughts?
>