90 Westy, 2.2 Gowesty WBX, Automatic

Going up a mountain pass on Interstate 90 in Montana, went up the pass at
the usual 50mph, crested the pass, then on the way down, the oil light and
buzzer went off for about a total of 20 seconds, then it went off on its own
while I was still driving.    NO room to pull over due to construction.
Light and buzzer remained off.    Pulled off an exit, checked the oil which
was fine ( closer to full).     Drove another 40 miles home, with no
problems, the van drove as normal, no oil buzzer or light.    The only
recent change to the van was a new water pump.

Any thoughts???

stan