Question for Paul McBride, the General Aviation News engines expert: I have an oil pressure issue I need help with.
When preparing for takeoff, the oil pressure indicator is in the lower green area during the pre-takeoff run-up. When starting the roll-out the pressure drops to just under the green and remains there when airborne.
The annual was done 1.5 hours ago and no problem was reported then.
The issue was found after a pre-buy inspection. I don’t think the issue was there prior to the inspection. The inspector troubleshooted the problem and was unable to resolve it.
I’m having trouble finding anyone who wants to handle this issue. The sale of the airplane is in escrow pending the resolution of the oil pressure issue.
Any comments or suggestions?
Thank you.
Mike Freeman
Paul’s Answer: Mike, thanks for your question and let me see if I can offer some advice that may help you and your maintenance facility find the problem.
I wish you would have provided a little more detailed information, especially exactly what was done during the recent annual inspection.
The reason that specific information is so important is because, as you mentioned, there were no issues prior to that work being done.
I’m going to take a “SWAG” — Scientific Wild A%@ Guess — at this and say I’d bet money that if this engine incorporates an oil pressure housing, when the screen was removed for inspection and reinstalled, the gasket was installed incorrectly.
The initial oil pressure on engine start-up is sufficient to puncture the gasket material, but not powerful enough to allow the normally seen oil pressure on the cockpit gauge. If this were the case, the engine probably suffered no damage and was supplied with enough oil pressure to sustain a safe flight.
On the other hand, if the engine is configured with a full-flow oil filter, we may still experience the same situation providing the oil filter housing was removed during the annual inspection.
Normally, this is not the case because the inspection usually just requires removing the oil filter and cutting it open to inspect for any foreign material. This is where any and all specific details of the annual inspection come into play, which I hope you can understand.
My best recommendation is to inspect the oil pressure screen housing gasket/oil filter base gasket for incorrect installation.
Not knowing exactly what was done during the annual, I see no reason for them to check the oil pressure relief valve on the rear of the crankcase behind the #3 cylinder, but if the seat for the oil pressure relief valve ball was not completely concentric on its seating service due to something passing through that area, that also may be something to check. But I have my doubts as to whether that’s the problem.
The best place to start is to review exactly what was done at the annual before beginning any troubleshooting and, if possible, talk to the technician who did the work.
My first check would be a different gage.
Don’t fly it !!!!! It can have pressure without volume ! Poor Hi-timer was killed at KPAE a couple years back because a screen was mis -installed.
Poor design,it should be impossible to install incorrectly.
Never disregard oil pressure !
Not enough information. Lots more questions than answers here.
For instance (not a guess on this issue), found a full flow spin on oil filter after 50 hours with no oil during change. I’d never seen that before in the past nearly 60 years, but it happened. All the oil for the time between changes was being bypassed. A filter defect. So yes, there is an answer, but not without a complete list of components.
Simply get more info, like ask the mechanic what he did. What engine is this?
Again not enough info……
VERIFY oil pressure readings with a known good MECHANICAL oil pressure gauge.
I’m with you. I always try the cheapest, easiest fix first. My first thought was a bad gauge.
Install a T- fitting at the the outlet for the sending unit and add an analog guage to the system. Common practice on hi-performace engines. At the very least it’ll show a bad guage.
How is the people operating? Does it hung or drift?
Is the oil corret? Is this a Twin. Are both engines showing same? Are all baffles and such in place?
Have oil been tested for metal
Jim, what do you mean by “How is the people operating?” And …
“Does it hung or drift?”
Yes Jim what are you trying to ask?