'87 B350 360 oil pressure problem

[mo71800]

'87 B350 van 360 engine. ex Navy recreation vehicle 88K miles, well maintained.

Twice in the past few weeks the lifters started to clatter and the oil pressure falls to the bottom of the scale. Upon stopping and checking, the oil level is at or above the full mark. When restarted, the oil pressure comes back up and clatter stops. It is a pressure problem not the gage.

The van is seldom used, maybe 1k per year and oil and filter are changed once a year.

I just flushed the engine with 1 qt of ATF in the oil and drove it about 20 miles. New NAPA filter and oil. No problems yet. Has anybody has a similar experience?

Some suggestions were:
too much oil and foaming
clogged screen
relief valve sticking (it is in the filter)

[B-300]

If the oil is foaming it will be evident on the dipstick (bubbles.)
The relief valve in the oil filter is a bypass to allow oil thru if the filter clogs.
Did you change the filter after flushing... It could be clogging.
A bad/worn oil pump drive could be the problem.

[alloro]

The most likely cause is sludge in the bottom of the pan. The suction from the pickup tube is pulling the sludge into the pickup screen and causing the loss of oil flow. When you turn the engine off, the suction is gone and the screen clears itself as the oil flows back down. That's why you have pressure the next time you start it.

[B-300]

Back in the days when built aircooled VW engines there were some oil pump manufactures that the oil pump gear would slip on the shaft when they heated up.... It's not likely, but is a possibility in you case.

[mo71800]

Just drove it 45 miles with new oil and filter-no problem!!!???? If it happens again. I'll carefully check the oil pan for sludge, but will not remove the pan.

[Dodgevanman]

Sounds like you just needed to drive the bejesus out of it to clear things out. :)

[mo71800]

It is used mostly to tow a 5,000 travel trailer, and the 360 really gets a work out. Hence the low mileage and yearly oil changes.

I just drove it 50 miles with the new oil and filter and had the usual excellent oil pressure. Go figure.