Oil pressure, oil filter, oil problems?

My first thought was the rislone cleaned a lot of gunk out of the engine, and the sludge plugged the filter.

An oil and filter change should have improved it, but I think 10-20 psi drop compared to before indicates that something else is wrong. I'd change the oil and filter again, and cut the filter open to see what you have in there.

I think you can use any filter that will screw on the adapter and seal, but you should not use a non-bypass filter on a non-bypass adapter. Not sure what adapter you have on your '86.

If you're holding 10 psi at hot idle on a 150K motor you're okay, as long as pressure comes up with rpm. As others suggested, the Rislone probably cleaned it real good, but that could be a blessing in disguise. It's not likely that the oil pump was cleaned, more likely some of the smaller passages were starting to get blocked. Getting oil to all the moving parts at low pressure is better than no oil!

I don't think I would run 20w50 in the winter, but then on a 150K motor it's not going to hurt a lot. You might want to run 20w50 spring through early fall, change to 10w40 for winter. If you don't drive it much in winter due to salt on roads and keep it in a garage I wouldn't worry much about running 20w50 in winter. It won't thicken that much even if the garage isn't heated. Might make cranking a little slower, just let it warm up 2-3 minutes before loading the engine (driving). I lived in southern Idaho years ago, had the same problems on those teen (and lower!) mornings, and I had a little Chevette diesel! Keeping it in the garage out of the wind made a tremendous impact on cold morning starts. You get a bit colder and stay that way a bit longer than Idaho, but many days are close.


Edited by farna - Apr/12/2012 at 10:15am

kensamc wrote:  Ron  Adapter or cover .... searching for gaskets, it's referred to more often as oil pump cover

Yeah -- the thing the oil filter screws onto -- bolted to the bottom of the front cover, covering the oil pump gears.

Oil pressure gets measured after the pickup/pump/oil filter/front cover. Any restriction in those, or increased "leakage" (bearing clearances, etc.) downstream from the pressure sender will register lower pressure.

Could be lots of things/combinations. Is the pickup screen now partialy plugged? Did the Rislone clean deposits out of the oil pump housing/gears that left it now pumping less volume? Is there gunk holding the oil pressure bypass plunger partially open? Gunk plugging the filter (even after oil/filter change)? Are the outlet passages from the oil filter/front cover into the block partially plugged? Did driving the vehicle for several days with Rislone-thinned oil clean deposits out of the oil galleys and other clearances? Did the thinner oil allow the crank/rod bearings to get hammered to larger clearances?

Is there gunk in the inlet to the pressure sender?

I'd pull the sender and make sure it's clean and working properly, then pull the pump cover and check the pressure relief plunger. Would also double check the gauge by temporarily plumbing in a mechanical one directly to the pressure port on the block.

I don't trust electric pressure gauges, period! The sending units get old and you don't know if it's right or not. The only good thing is I've never seen one read oil pressure when there isn't any. As they age they usually read low or fail altogether. They are better than an idiot light only, but not much more!