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Low Oil Pressure - Upper Galleries Plugged?
I've been working on my daughter's car; a '92 Cutlass Supreme SL with a Gen II 3.1L MPFI V6, which has about 150k miles. If you don't have time for the whole background story, please jump ahead: my question is the last sentence of the last paragraph.
While she worked for peanuts and we were unable to help her make ends meet, this car soldiered along without an oil change for over 40,000 miles. (Yeah, I know! Poverty sucks!) When money finally allowed I changed the oil and filter; the blackish-brown oil was the dirtiest I'd ever seen.
About two days after this oil change the oil pressure (which had always been well over 60psi,) suddenly dropped, lifters rattling and 10-15psi at most showing on the gauge. Suspecting a filter plugged by newly circulated sludge, I replaced the filter again. This allowed the pressure to improve, but only to about 20psi and only for a few minutes. It quickly dropped back down to 10-15psi, so I replaced the filter a third time, which yielded no change at all.
I bought a new oil pump, dropped the sub-frame and pulled the pan, finding the crankcase unbelievably clean. Understandably there was a little bit of ash in the bottom of the oil pan, but the block was a sparkling gray and the pistons and rods were still bright and silvery. Everything looked absolutely brand new - I'm still amazed. Anyway, the rods felt just loose enough on the crank journals to merit suspicion, so I removed the rod caps and bearings. I measured the crank journals; all checked out great. The rod bearings I took out looked almost new. The oil pump screen was not at all blocked, and when disassembled, the old oil pump looked fine.
I installed the new oil pump and new rod bearings for good measure, and although the old oil pump driveshaft looked nearly new, I replaced it anyway because a new one cost less than $2. When I primed the new pump with an electric drill, oil surged out of the engine block (where the oil filter block attaches.) Encouraged, I reassembled everything, thinking we'd be back in business. No dice. Only 10-15psi, as before, lifters still clattering away.
With that failure behind me, my best guess now is that the new (as in "first-in-40k-miles") oil filter briefly allowed a higher oil pressure, which maybe moved some accumulated sludge or ash into an oil gallery above, plugging or severely restricting oil flow up on top. Aside from driving the car around the lawn for a minute or two every few weeks, it's been parked. We can't presently afford to rebuild or replace the engine ...or the car.
While I can just hope our treasure ship will come in, is there anything left I can do short of pulling this engine and completely dismantling it? (I can't presently afford even a gasket set.) If the engine's merely unbolted from the bellhousing and hoisted a few inches, will that expose any gallery endplugs I might remove (to employ a coat hanger wire or some bore-brushes or something?)
While she worked for peanuts and we were unable to help her make ends meet, this car soldiered along without an oil change for over 40,000 miles. (Yeah, I know! Poverty sucks!) When money finally allowed I changed the oil and filter; the blackish-brown oil was the dirtiest I'd ever seen.
About two days after this oil change the oil pressure (which had always been well over 60psi,) suddenly dropped, lifters rattling and 10-15psi at most showing on the gauge. Suspecting a filter plugged by newly circulated sludge, I replaced the filter again. This allowed the pressure to improve, but only to about 20psi and only for a few minutes. It quickly dropped back down to 10-15psi, so I replaced the filter a third time, which yielded no change at all.
I bought a new oil pump, dropped the sub-frame and pulled the pan, finding the crankcase unbelievably clean. Understandably there was a little bit of ash in the bottom of the oil pan, but the block was a sparkling gray and the pistons and rods were still bright and silvery. Everything looked absolutely brand new - I'm still amazed. Anyway, the rods felt just loose enough on the crank journals to merit suspicion, so I removed the rod caps and bearings. I measured the crank journals; all checked out great. The rod bearings I took out looked almost new. The oil pump screen was not at all blocked, and when disassembled, the old oil pump looked fine.
I installed the new oil pump and new rod bearings for good measure, and although the old oil pump driveshaft looked nearly new, I replaced it anyway because a new one cost less than $2. When I primed the new pump with an electric drill, oil surged out of the engine block (where the oil filter block attaches.) Encouraged, I reassembled everything, thinking we'd be back in business. No dice. Only 10-15psi, as before, lifters still clattering away.
With that failure behind me, my best guess now is that the new (as in "first-in-40k-miles") oil filter briefly allowed a higher oil pressure, which maybe moved some accumulated sludge or ash into an oil gallery above, plugging or severely restricting oil flow up on top. Aside from driving the car around the lawn for a minute or two every few weeks, it's been parked. We can't presently afford to rebuild or replace the engine ...or the car.
While I can just hope our treasure ship will come in, is there anything left I can do short of pulling this engine and completely dismantling it? (I can't presently afford even a gasket set.) If the engine's merely unbolted from the bellhousing and hoisted a few inches, will that expose any gallery endplugs I might remove (to employ a coat hanger wire or some bore-brushes or something?)
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