---- John Rodgers <inua@CHARTER.NET> wrote:
>   While driving my manual tranny 88GL  home this afternoon the oil
> pressure alarm sounded and the oil pressure light came on. I killed the
> ignition immediately, noted all the gages seemed normal, and being very
> close to my house just  coasted on down the street, around the corner,
> and halfway up my up-slope driveway and stopped. All the while I'm
> thinking "Omigosh! What now?" ( I have an important art show to
> participate in on Sat. and have to set up by 6 am -- this is not good!)
>
> After getting stopped, I sat for a moment, the turned the ignition on.
> All the lights did their normal thing. I hit the switch, the engine
> started right up, oil pressure light went out. I noted no strange
> sounds, and the oil pressure alarm did not sound. I drove the remaining
> 100 feet  up the hill to the house - all was normal.
>
> Today was extraordinarily hot - 100 plus degrees, driving was slow
> coming off the highway home, and even though the temp gauge needle was
> in the middle, nothing seemed wrong. I did note that at very slow speeds
> the fan kept coming on frequently. I was poking along about 30 mph when
> the alarm sounded and the oil pressure light came on.
>
> I opened the hatch, and noted the engine seemed really hot. The heat
> just came boiling out. I looked for oil leaking, coolant leaking, etc,
> but found nothing. Oil dip stick measures halfway between the marks, and
> the coolant level is up. I checked the rear oil pressure switch, and the
> wiring connector, but it was tight.
>
> I let the van sit a while with the hatch open to cool the engine, then
> started it up. After Idling a minute, I revved the engine up to 3000. I
> ran perfect. No lights, no alarms. I have tried several times now, but
> cannot reproduce the event. Of course the circumstances have changed as
> the atmosphere is cooling down.
>
> Anybody have any ideas? Can the engine oil get so hot under normal
> driving conditions as to cause low oil pressure. Surely that is not a
> good thing. But how can I avoid that in the common daily summer weather
> here in the South. I'm afraid this event might repeat itself at a
> tremendously inopportune time - as such events usually do.

John, all engine oil thins out with heat, whether multi-grade or not.  My understanding is that the waterboxer cannot keep the oil cooled enough to avoid this situation.  I assume you use a good 15W50 or 20W50.  I have had a similar situation, but would get a warning light only when slowing from speed to idle.  It would occur under very hot ambient temperatures, usually over 100 F, and when I had been driving at highway speed.  I However, I have an oil pressure gauge, and the pressure would drop to around 15 psi at 3500 rpm in 4th gear.  Last summer I learned that entering cooler air resulted in an increase in oil pressure, sometimes a dramatic change, as when I encountered a thunderstorm on Raton Pass last summer.

I installed a tencentlife external oil cooler.  Problem seems gone, though I have not hit the road yet this summer (but we are forecast for 100 F tomorrow, about a month early this year).  When I've driven in low nineties F temperatures before the external oil cooler, the oil pressure would generally run around 22 psi or a little lower.  Now it runs around 40 psi with the external cooler.  I consider it a great buy.

mcneely