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Zero Oil Pressure

Mark Dickens

Well Known Member
Patron
Oil pressure (as measured on my Dynon Skyview) went to zero last evening on the ground while testing the installation of my new CS prop. I had done a couple of run ups, exercised the prop, etc and then got a warning from Skyview. I taxied the 200 yards back to the hangar while watching the oil temps and CHTs. By the time I got there, the indicated pressure was zero and I shut down quickly. Oil temps and CHTs were all about what they were before the warning (121F for oil, mid 300s for CHT), so in looking for corroborating information that I really had an oil pressure problem, I wasn't able to find it.

No oil loss, no oil leaks, dry as a bone FWF. I did do an oil change very recently and had 7 qts in the engine. I send oil samples to Blackstone at every change and I had a great report from them on this change. The engine has about 200 hours on it, a Titan IOX-370.

So, need a plan to figure out what's happening. One obvious possibility is a bad oil pressure sensor (it's the Kavlico sold by Dynon). So, plumbing in a mechanical gauge makes sense and then I'd remove the top plugs and run the starter with ignition off to see if I get a pressure indication. Another idea is to remove the oil pressure line and fitting to check for obstruction. If none of these point to the answer, what's next (other than a teardown)? Ideas?
 
Mark---DEFINIATELY plumb in a remote oil pressure guage and check the pressure. Not sure what else has been done as far as making any changes that 'might ' have created an electrical issue. Rare to have real oil pressure just go away like that.
Let us know!!

Tom
 
I am a firm believer in a mechanical and electronic oil pressure gauges. Easy to install mechanical one. :cool:
 
You might also consider checking the crankshaft plug, since you said you have a new CS prop, to make sure it is properly installed. Especially if you changed from a fixed pitch prop.
 
You might also consider checking the crankshaft plug, since you said you have a new CS prop, to make sure it is properly installed. Especially if you changed from a fixed pitch prop.

Fortunately, Titan installed a rear plug with the threaded boss for a pipe plug, so all I had to do was install that. Pardon the probably dumb question but if the pipe plug came uninstalled somehow, how would that affect the engine oil pressure? Wouldn't it just drain back into the crankcase?
 
I still haven't solved the mystery, but the plot thickens. I bought a Harbor Freight mechanical oil pressure gauge and it showed 0 PSI as well, so that seems to exonerate the Kavlico oil pressure sensor. I drained the sump and removed the oil screen and it was normal (few specks of carbon). Because of the low engine time and historical reliability of these oil pumps, I was skeptical that the pump was the problem and decided to start the engine and watch the oil temps and CHTs to see if anything untoward popped up, and after two separate starts, running up to as much as 2300 RPM, everything was good. CHTs were normal and the oil cooler was hot when I shut down, so oil was being pumped. Still the sensor reported 0 PSI.

Now here's where it gets interesting. First, I can't exercise the prop any longer and second, the oil temps basically got to ambient and sat there with no rise.

My hypothesis is that the pipe plug I installed in the rear crank plug has come out and this is why the prop is not responding to the governor. But would this also affect the 0 PSI reading on the oil pressure sensor and the flat oil temp?

I've been pouring over Lycoming's docs this afternoon, but have come up empty. Any input from the real engine gurus?
 
wow!! zero op on a mechanical guage and 2300 rpm? Twice? My advice is disconnect the oil cooler line from the center of the accessory housing. That port goes directly into the oil pump output. Crank the engine with the spark plugs out and see if you even had flow. If not, don't worry about the problem you will find it during the complete teardown. Dangerous troubleshooting plan you had....
Good Luck,
Mahlon
 
Undo what you did

I once had a mechanic who was helping me get my A&P say if the engine quits after gear retraction what should you do? Answer, undo what you did and put the gear back down. Incidentally this was just down the road from you at the old Arlington airport that is now gone.

You installed a new propellor that is in the oil system. First thing to do is remove the prop and governor. Something isn't right in that system most likely. And definitely don't run the engine with no oil pressure. That's an expensive troubleshooting technique!

Tommy
 
I once had a mechanic who was helping me get my A&P say if the engine quits after gear retraction what should you do? Answer, undo what you did and put the gear back down. Incidentally this was just down the road from you at the old Arlington airport that is now gone.

You installed a new propellor that is in the oil system. First thing to do is remove the prop and governor. Something isn't right in that system most likely. And definitely don't run the engine with no oil pressure. That's an expensive troubleshooting technique!

Tommy
The old Arlington airport was real handy for those of us based at Charles Baker, 2M8. When the weather was low we would shoot the approach at Arlington and then perform what we called the Loosahatchie transition. Following the Loosahatchie river would put us on a right base for rwy 36 at 2M8. My first engine overhauler, John Jewell, was located at Arlington. He moved to Holly Springs when they shut the airport down.
 
Mea culpa. I performed Mahlon's test this morning and just a dribble, so I'm in for an expensive lesson. I think what may have happened is that the pipe plug installed in the crankshaft plug came out during my run up and prop test, affecting oil pressure. What I shoulda done is obvious now. I've rendered my garments, donned sackcloth and am sitting in ashes....

So, a call on Monday to Titan is one of the first things on my list. Hey it could have been a lot worse, I could have been in the air. Thanks to all for your input.
 
So, so sorry that this happened, Mark. So, so thankful that it did not happen on takeoff!

Ron B
 
Wouldn't an open orifice in the system act like your pressure relief depending on location? You should have some registering oil pressure on a functioning gauge and flow when opening via Mahlon's post.

This sounds like you truly had almost no oil pump function.
 
Remove the oil pressure relief on the back right cylinder and look to see if the ball is seated properly. On a flight south last year my buddy called low pressure and landed at a very close airport.
We checked everything and then went to town an purchased an auto mechanical gauge with a selection of brass fittings. Checked and found no oil pressure
Drained the oil and found no metal in the oil or fitting. Then we pulled out the oil pressure setting bolt and low and behold fond a small 1/8? piece of an aluminum fitting stuck in the seat of the oil pressure riel for valve

Removed the piece and all was well. Years ago he had a fitting crack on the oil cooler and a small piece had stayed in the system somehow and finally moved
 
Unfortunately, I've already looked at that...no obstruction. I believe that the pipe plug worked its way out during the prop test. Because of the holiday, no time to pull the prop, but will this week and verify. I don't see any reasonable alternative to tearing it down and am expecting to do that soon. Thanks to all for thoughts, but ultimately, it's my mistake.
 
I?m confused how the crankshaft pipe plug could be the problem. In a fixed pitch plane, that plug is removed which opens the front chamber of the crank to the crankcase
 
I?m confused how the crankshaft pipe plug could be the problem. In a fixed pitch plane, that plug is removed which opens the front chamber of the crank to the crankcase

I converted to CS and installed the plug. If it came out (which I'll know for sure this afternoon), oil pressure would have plummeted as it was pumped back into the crankcase.
 
Scary

Mark,
I'm so sorry this happened. I've had my prop for a few weeks now and been waiting for the right time to put it on and been following your progress as well. I hate that you are going through this issue. I wish you the best and least expensive repairs :)
 
Well, it turns out that the pipe plug in the rear crankshaft plug did NOT come out. I was very surprised to see it right where it should be. So, unless someone can give an alternative explanation, it appears to me that my less than 200 hour Titan IOX-370 engine had a complete oil pump failure. Good thing it was on the ground. I'll be calling Titan tomorrow
 
Keep us other 370 owners updated on what the final result is, curious minds want to know.
The 370 oil system is exactly the same as the 360 which has decades of proven reliability.
 
Any chance that a bad governor could vent the oil back into the crankcase and cause the pressure loss?
 
A Head Scratcher

I do have a little mystery in all this, and perhaps one of the real engine gurus can explain it. When I unwisely did my additional runups after the PSI indicated zero, at the conclusion of the runups, I put my hand on the oil cooler. It was hot in every case. How does an oil cooler get hot (not warm, hot) if an oil pump has failed? I'd dearly like to understand that.

Edit: For clarification, these runs were the next day after the oil pressure had fallen to zero, so the engine started off cool.
 
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Oil pump

I would doubt the oil pump failed. Since you added a governor and the plug, one of them is almost certainly the culprit. Maybe the wrong gasket under the governor. I don't know, but a failure of the pump immediately after adding a system that changes the oil flow... Hmm!
 
I would doubt the oil pump failed. Since you added a governor and the plug, one of them is almost certainly the culprit. Maybe the wrong gasket under the governor. I don't know, but a failure of the pump immediately after adding a system that changes the oil flow... Hmm!

I had two separate and successful test runs before all this happened. Prop exercised properly, everything was good. I used the gasket that Whirlwind included with the governor (see https://www.aircraftspruce.com/catalog/eppages/propgovgasket.php for a pic. I don't know how it would work fine and then not work. I agree with you that the timing of all this is suspicious, but I can't figure it out.

Edit: the pipe plug was in place much to my surprise...so that's not the issue
 
I'm going to grab an oil sample and ship it to Blackstone for analysis, Fortunately, I'd just done an oil change before all this occurred, so I'd expect to find high metals from wear.
 
Have you removed the oil pressure relief valve and inspected for debris under the ball?

Bill

I did remove the valve to inspect it, but I probably didn't inspect the ball seat as well as I should have. I'll do that this afternoon. Nothing was visible but again I didn't get down and really hawk it
 
I did remove the valve to inspect it, but I probably didn't inspect the ball seat as well as I should have. I'll do that this afternoon. Nothing was visible but again I didn't get down and really hawk it

Is it possible something has gotten into the sump (rag) that could be blocking the oil pick-up tube?

Skylor
RV-8
 
I did remove the valve to inspect it, but I probably didn't inspect the ball seat as well as I should have. I'll do that this afternoon. Nothing was visible but again I didn't get down and really hawk it

I did it again this time with a flashlight and magnet. Other than a microscopic sliver of metal about the size of a small hair, nothing was found. I don't think this is the issue, unfortunately.
 
Blown gasket on the governor? Can it bypass that much oil in that case?

Another good question I can't answer but I can think hard about. As frustrating as this has been, it's been a puzzle to solve, and I like doing that. I still do not understand how the oil cooler gets hot if the oil pump is dead...
 
no oil flow out of the pump from that fitting will not produce metal in the filter or at the relief valve. There was no flow. that fitting goes directly into the oil pump output port. No flow there no flow anywhere. Either the oil pump failed or the suction screen is blocked. Nothing down stream from the pump could cause no flow out the center oil cooler fitting. BTW Mark the plug missing from the rear on the crank shaft nose section will not cause zero oil pressure. The prop won't work so good but you would still have pressure. Also, even with the relief valve ball out of the engine, you will still have about 50 psi oil pressure at power. Really low at idle but you would still have pressure.
Why was the cooler hot? Can't say. Hot air from the cylinders blowing on it? In a normal situation, there is just a very little flow through the cooler if you have a vernatherm installed until you get the oil to temperature (150- 165F plus). If you did a couple of quick runs to power from cold status, the oil cooler wouldn't normally get any flow, until you got the oil pretty hot. So the cooler wouldn't start to get hot from oil flow until you had at least above 150f oil in the sump.
Hope there was enough residual oil on the bearings and at the front thrust surface to have prevented any serious damage but the only way to tell for sure is to look. Especially at that front thrust area of the case and shaft, really susceptible with no oil flow there.
Good Luck,
Mahlon
 
At this point, it seems to be only a matter of choosing an engine shop. I have a quote from Continental/Titan. I will be getting at least two others. Barrett will be one of them. Recommendations are welcome. PM if you want.

Thanks to Mahlon for his input. I do have the Dynon data logs at the office and will take a look at the CHTs to see if heat from the #2 and #4 cylinders could have heated the cooler up, but it's really no matter since the engine has to be looked at. It's really more a matter of curiosity at this point.
 
Do you know if your oil pickup tube is attached to the lower face of the accessory housing? Most older Lycoming o-320s use this type of pickup. perhaps the safety wire was not installed and the screws backed out and the pickup tube fell off the accessory case mount. Just another way you could end up with 0 psi oil pressure. Being your engine is a new 370; I don’t think they use this configuration of oil pickup. Could be wrong though.

Bill
 
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That's an interesting question. I don't know how I'd determine that without pulling the accessory case cover off
 
Firstly Mark, best wishes for a good outcome on whatever you find inside your engine. I am following this thread with interest and I do have a query for Mahlon if he is still watching.

My advice is disconnect the oil cooler line from the center of the accessory housing. That port goes directly into the oil pump output.
In a normal situation, there is just a very little flow through the cooler if you have a vernatherm installed until you get the oil to temperature (150- 165F plus). If you did a couple of quick runs to power from cold status, the oil cooler wouldn't normally get any flow, until you got the oil pretty hot.
I am not understanding Mahlon's logic with regard to oil flow from the output at center of accessory housing in relation to a Vernatherm installed. Does the Vernatherm restrict oil flow returning from the cooler rather than to it? From my engine's (0320 D2J) parts diagram I see the Oil Cooler AN Fittings on the pump output and return just below the breather. The Vernatherm is shown installed as part of the Oil Filter Adapter and I don't see the relationship to the Oil Cooler curcuit? Having just installed a B&C right angle filter adapter and currently fitting the oil cooler I need to fully understand how it works. Any further info or clarification much appreciated.

Regards, Russell
 
If the hex plug in this photo (shamelessly grabbed from a google search) fell out and the oil level was below the plug the oil pump would be sucking air.
Just a thought and not sure if the Titan has the plug but I believe it does.

SuperiorSumpGasket.jpg
 
Firstly Mark, best wishes for a good outcome on whatever you find inside your engine. I am following this thread with interest and I do have a query for Mahlon if he is still watching.



I am not understanding Mahlon's logic with regard to oil flow from the output at center of accessory housing in relation to a Vernatherm installed. Does the Vernatherm restrict oil flow returning from the cooler rather than to it? From my engine's (0320 D2J) parts diagram I see the Oil Cooler AN Fittings on the pump output and return just below the breather. The Vernatherm is shown installed as part of the Oil Filter Adapter and I don't see the relationship to the Oil Cooler curcuit? Having just installed a B&C right angle filter adapter and currently fitting the oil cooler I need to fully understand how it works. Any further info or clarification much appreciated.

Regards, Russell
Hi Russell,
When the oil is cold, there is oil pressure down the lower oil cooler hose from the pump to the cooler. At that time, the vernatherm is porting the upper oil cooler hose to the same oil pump output pressure and that same upper port the vernatherm is leaving open, is supplying the engine with oil pressure and at the same time, also supplying the cooler with oil pump output pressure. There is no flow because both hoses and ports to the cooler have the same oil pump output pressure going to them in the direction towards the cooler. The oil cooler is in parallel with the engine and has no flow because there is no pressure differential between the two hoses and ports that would supply the cooler. the oil flow is out of the pump, to the filter, to the engine with the cooler bypassed. As the oil heats up, the vernatherm starts to close . The porting of the upper oil cooler hose, changes from being in parallel with the engine to be in series with the engine. Now, the oil flow is out of the pump down the lower hose through the cooler and back into the engine through the upper hose. At the point the oil now goes to the filter and the rest of the engine.
So the flow is out of the pump, through the cooler, through the filter, to the rest of the engine.
The vernatherm has a spring loaded bypass so that when it is in the closed position, with hot oil, should the cooler become plugged, the bypass will open to allow flow to the rest of the engine by porting the oil like there was cold oil.
To confuse things , just a bit, when the oil is cold there is actually a very small amount of flow through the cooler to prevent oil from congealing in it, during extreme cold weather operation. Very, very limited flow but it is there. Thus, if you flew for hours at high altitude, where it was very cold and the oil temp was really low, the cooler would be off line due to the cold oil. during this type of operation, the cooler wouldn't plug up with very cold oil due to the lack of flow because of the very limited flow through the cooler that is allowed when the oil is cold. And when you lost altitude and the ambient got warmer and the oil temp went up to normal the cooler would be functional and not plugged with cold congealed oil, due to the limited flow that was allowed to keep the oil in the cooler from congealing. Hope this helps and you understand it.
Good Luck,
Mahlon
 
For anyone bored enough to continue following this saga, I've chosen to send the engine back to Continental/Titan. They shipped a crate yesterday and I should have it today. Scott Welch at Continental has been very easy to work with and very responsive to questions. I probably could have saved a few bucks with a different shop, but I think you generally get what you pay for.

I should have the engine back in about 6 weeks +/- after I ship it. I think I know how I will be spending Labor Day. More later...
 
Mahlon, thanks for an explanation that even I

could understand! I (we) really appreciate your input on the forum!

Ron
 
Pressure

Plug, check crank plug. At least pull spark plugs,
Motor engine and look for oil flow.
DO NOT RUN ENGINE until you get
Pressure!!!!
 
Thanks Mahlon, Your explanation helps enormously and I understand it now. I have more wonderings about the Vernatherm but that would be for another thread. Thanks again.

Mark, please let us know what you/Titan find. It is a tough way to find out how a Lyc fares without oil pressure but it is interesting.

Regards,
Russell
 
I pulled it early in the process. 1-2 very small carbon specks. I showed it to a local A&P/IA who happened by the hangar and his comment was "that's normal".

You are positive that you looked at the SUCTION screen? Not the PRESSURE screen or filter? I initially thought the same as another commenter.. perhaps a rag got into the prop hub, and pieces are moving into the governor screen and into the oil sump. You said all of this happened after installation of the CS prop.. have you pulled the governor and looked at the oil passages there? Man. .running the engine for several minutes with no oil pressure, two guages, and then doing two run-ups? Sounds like you need to surrender your toolbox and hand the keys to an engine shop! Lol Good luck and keep us posted!
 
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