Any idea why oil pressure would decrease on factory gauge when RPM increases? Recently had an older Turbonetics T63 turbo implode and it was replaced with a brand new Precision turbo, which now has bearing play after the oil decrease event a few days ago. No weird engine noises or anything else. The shop is working through the issue but I'm curious if anyone has ever experienced something similar or has any input?
Oil Pressure Decrease with RPM Increase
- Thread starter aviator31
- Start date
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The oil pressure should not go down while the RPM increase. I would have the shop attach an actual gauge and monitor so you have real data. You also reference an "oil decrease event" which might also give you your answer.
- Thread starter
- #3
Good advice and I should’ve clarified that it was oil pressure decrease, not quantity.
Has the Harmonic balancer (front crank) bolt been off for service (harmonic balancer, oil pump cover leak, front crank seal replacement) recently?
If an actual (dial type) oil pressure gauge hooked up to the oil pressure sensor port shows a pressure drop one quick test might be to replace the oil filter to eliminate the possibility somethings happening (collapsing internally)?? If you think it's the oil filter do not cut it open if it caused damage to your engine, seal it into a bag, call the filter manufacturer, follow their recommendations and ship it to them. Document with photos of the filter on the engine, being removed from the engine, and then being placed directly into a sealed bag with mechanics signatures along the way, -----
IIRC someone many years ago had a low oil pressure issue with one of the oil pressure relief valves
FWIW:
If an actual (dial type) oil pressure gauge hooked up to the oil pressure sensor port shows a pressure drop one quick test might be to replace the oil filter to eliminate the possibility somethings happening (collapsing internally)?? If you think it's the oil filter do not cut it open if it caused damage to your engine, seal it into a bag, call the filter manufacturer, follow their recommendations and ship it to them. Document with photos of the filter on the engine, being removed from the engine, and then being placed directly into a sealed bag with mechanics signatures along the way, -----
IIRC someone many years ago had a low oil pressure issue with one of the oil pressure relief valves
FWIW:
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@aviator31: ---an older Turbonetics T63 turbo implode---"
What exactly happened to that Turbo?
Any other major work on the engine (complete rebuild) previously?
Has there been any work involving (removing/installing) the harmonic balancer/crank bolt before the low oil pressure issue began?
If the crank bolt is not torqued correctly (304 ft lbs) you can lose oil pressure. There's a gear behind the harmonic balancer and lower timing
chain sprocket that drives the oil pump which is held tight or "pinched" in place by that bolt. If the crank bolt has not been torqued down that gear can slip and subsequently not drive the oil pump as designed.
Some random thoughts FWIW:
Has the shop confirmed low oil pressure?
Is the Engine oil level full?
Even with a Toyota oil filter it wouldn't hurt to replace it, just to eliminate that possibility
Has the shop pulled the pressure relief valves for inspection?
You could also send a sample of used engine oil to Blackstone Laboratories for an Engine Oil Analysis ie: if the rod or main bearings
are wearing enough to lose oil pressure it might show up in the oil analysis (increased wear metals).
What exactly happened to that Turbo?
Any other major work on the engine (complete rebuild) previously?
Has there been any work involving (removing/installing) the harmonic balancer/crank bolt before the low oil pressure issue began?
If the crank bolt is not torqued correctly (304 ft lbs) you can lose oil pressure. There's a gear behind the harmonic balancer and lower timing
chain sprocket that drives the oil pump which is held tight or "pinched" in place by that bolt. If the crank bolt has not been torqued down that gear can slip and subsequently not drive the oil pump as designed.
Some random thoughts FWIW:
Has the shop confirmed low oil pressure?
Is the Engine oil level full?
Even with a Toyota oil filter it wouldn't hurt to replace it, just to eliminate that possibility
Has the shop pulled the pressure relief valves for inspection?
You could also send a sample of used engine oil to Blackstone Laboratories for an Engine Oil Analysis ie: if the rod or main bearings
are wearing enough to lose oil pressure it might show up in the oil analysis (increased wear metals).
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- Thread starter
- #7
All great points and suggestions, thank you. They were planning to troubleshoot a number of the items you highlighted. I will follow up with the findings when I learn more.
60wag
SILVER Star
A pressure decrease with a pump speed increase sounds like restriction to the pump inlet. Id start with the pickup sceen in the pan and work towards the pump looking for an obstruction.
Fj80oregon
GOLD Star
Check the pressure with an actual gauge! You can’t trust a 30 year old gauge or sender in your truck. No reason to chase your tail if you don’t have a actual reading.
@aviator31 : can you answer any of the questions above ie: what you know (?oil level) or did you just have it towed to the shop and they haven't started work on it?
Can you list what work has been done to the engine before this happened?
Can you list what work has been done to the engine before this happened?
If I had the ability to connect the dots, it was erratic to the low side movement in the oil pressure gauge that we should have interpreted as a signal our harmonic balancer was failing. In these early stages the HB looked okay but in retrospect the inner bit was rotating and the belts were behaving erratically. Later on we spotted things when the outer pulley ring was physically moving 3/8" towards the radiator.
Perhaps a picture is useful, the new and old together. This is a low use vehicle so it happened over less that 500 miles, but five months of driving.
- Thread starter
- #12
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- Thread starter
- #13
Well it looks like a new short block and rebuild is in my future. Not sure what happened, no indication of any motor issues whatsoever and the truck has been well maintained over the last 11 years I've owned it. Thought these things were "bulletproof" but I guess it is nearly 30 years old and has 200k miles on the clock. Hey, at least it will be baselined now lol.
mudgudgeon
Resident galah
What was damaged?
- Thread starter
- #15
Not certain yet but metal in the oil filter after they cut it apart.
