[T2] Unsteady oil pressure and temp

[Sami Dakhlia]

Hi,
In what's a first in many years, I managed to drive my '75 Westy from
LA to the Bay Area without any incidents. Stretched the trip out over
two days, with an overnight stay at Montaña de Oros. As always, a
lovely spot: the rocks, dunes, eucalyptus trees, the ocean, and the
breeze, great hiking trails.

Got up before sunrise this morning (still Euro-jet lagged) and decided
to drive the remaining 220 miles to destination while the weather was
cool. I have VDO gauges for oil temp and oil pressure and although I
don't expect scientifically accurate readings, I tend to keep a
vigilant eye on them, every few minutes.

Here's what I found odd: after a good hour of driving, oil temp
slowing climbed to the 240F mark, while oil pressure remained steady
at around 24 psi. (The figures are approximate.) Then the pressure
reading suddenly dropped to about 18 psi and the oil temp dropped at
well, down to 220F over the next couple of minutes.
An hour later, the opposite happened, the pressure went up to 24 psi
and oil temp crept up to 240, then 250 F. (At which point, I pulled
over and let things cool down.)

I'll add that I've been driving at a steady 55mph, that the weather
was cool (in the 60's this morning, then high 70's), and that I'm
running 15w50 mobile 1 fully synthetic oil.

Hypotheses?
I've got two, not mutually exclusive: (1) the distributor is worn out
and randomly shifts the advance curve; (2) the oil pressure relief
valve by the oil cooler is sticky.

But it's great to be back in California!

Sami