Low oil temperature during flight

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Carlos MV

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Hello Everyone,

For this thread is important to mention I live in Panama City (Central America) and the weather here is 80ºF to 95ºF all year round. I fly a 1980 C182Q with recently installed all-six brand new Superior Millenium cylinders in February this year. After the cylinder change, as expected, the engine was running somewhat hot according to the instrumentation I had then (JPI EDM-700 and the original Cessna engine Instruments). Oil temperature would indicate anywhere between 190ºF - 200ºF and CHTs were above 400º on some cylinders steady during the entire trips. I flew like this for about 50hrs up until June when it went in for a panel upgrade.

Now I have upgraded my instruments to an all-glass Garmin G3X panel with new probes the values I see indicated have changed a lot. The indicated oil temperature is now very low while flying and the CHTs are also lower but not alarming lower.

The oil temperature is now indicating Between 122º and 130º in level flight at 6K-7K-8K feet with cowl flaps closed and leaned properly with lean assist. The highest it goes is 145º in climb out with full mixture. Cylinder head temperatures are in fairly reasonable range (340º the hottest, 210º the coolest in level flight at 65% power setting).
It it important to mention I removed, fixed and painted all engine baffles and put brand new baffle seals and so this may have helped reduce all temperatures but I still see the change too drastic.

So, I removed the oil temperature probe and tested it in water with a handheld thermometer and it indicates precisely as the thermometer did. Next I removed the vernatherm and checked it in hot water and, as it should, above 70ºC I noticed the contraction. The only thing I'm left without knowing is if when expanded it is fully expanded. Other than that I don't know what could be happening.

If anyone has any thought or ideas please share here.
 
Carlos MV said:
Next I removed the vernatherm and checked it in hot water and, as it should, above 70ºC I noticed the contraction.
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It's supposed to expand (get longer) as the temperature increases.
 
Carlos MV said:
Now I have upgraded my instruments to an all-glass Garmin G3X panel with new probes the values I see indicated have changed a lot.
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A rule of thumb is to go back to the last thing you did and find out why that made a change (see post # 2) ...
 
RyanB said:
So the only thing that changed was the panel upgrade and then it suddenly started to run cold?
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I wouldn’t say it is the only thing that changed since I also fixed the baffles and the seals.
What catches my attention is the big change. The new oil temp is now extremely low. I have to assume the indications are good since I tested the probe and it was good. That’s what has me dazed.
 
Carlos MV said:
I wouldn’t say it is the only thing that changed since I also fixed the baffles and the seals.
What catches my attention is the big change. The new oil temp is now extremely low. I have to assume the indications are good since I tested the probe and it was good. That’s what has me dazed.
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Have you got it programmed for temperature in Celsius instead of Fahrenheit?
 
You have some big splits in nearly every measurement. I would start by checking every connection, especially grounds in the system. Make sure you have the correct probes and the Garmin setup is correct for the prove type.
 
The differences in CHT tell me something isn’t right. Also if oil temp was accurate, 130 would never boil off the moisture in your crankcase. I guarantee it’s not accurate.


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Peter Anderson said:
The differences in CHT tell me something isn’t right. Also if oil temp was accurate, 130 would never boil off the moisture in your crankcase. I guarantee it’s not accurate.


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What do you consider should be an adequate difference in CHT indications?
 
I recall during some past reading what expected CHT or EGT splits should be on the subject engine. Anyone want to suggest at what point would the split be more than expected?
 
I’ve read reports of odd temperature indications related to the omission of a reference thermocouple during installation.
 
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you really want the oil between 180-200 ideally and that should be easily reachable in cruise even at modest RPM.
It is important to have the oil high enough, but not too high of course to burn off and vaporate any moisture that can cause corrosion on the ground.
your CHT's are also very low for what I considered/thought to be normal. At a normal combustion you'd easily see them in the 300's especially during OAT's of 70/80
as you were flying...

I'd say the calibration or location of the sensors are not correct and I would have it rechecked.

Interestingly I wrote about this just a few hours ago as I couldn't get my head around my EDM numbers and sure enough it appeared the wirings were on the wrong cylinders. I am not saying but it is possible there is an installation correction needed.

in summer MA I run about CHT 350 +/-10 on all 4 (200 hp lycoming io 360 c1c) at 55% rated HP leaned down to 45% (is 50-70 LOP) (is 22"MAP/2150RPM@2000) oilT 190-195F

ps nice panel you have!! :)
 
Thank you all for your great input.
Yesterday I had the shop check everything with the probes installation and programming. They say all is good.
The oil temperature probe was replaced with a brand new one (even though the other one was brand new as well) and in a ground run it now seemed to indicate good as for the first time I saw readings above 150*. After about 15 minutes running it at 1500 - 2000 RPM the oil temperature wen to 172*.
i closed the cowlings and wen to the air to find the same old (Even worse). My oil temperature was again below 120* all through the flight Including the climb.
my question is, could it be a damaged vernatherm? Could the CHT issue be a consequence of the low oil temperature?
Thank you all for your help!

IMG_5267.jpeg
 
Your gauges are wrong. Vernatherm or not, there is NO way at 23 inchs and 2300rpm at 69F OAT that oil can be 112F. your engine is 30-35%% efficient. the rest is waste heat. you are burning 10.5gph at 125000btu per gallon. meaning you have about 850,000 BTU/hr of waste heat. You have a poorly calibrated new fancy system.
 
I would have to agree. Your instrumentation is wrong. It is literally impossible for oil in a warmed up, operating aircraft engine to be 43F above an ambient temp of 69F. Your CHT's look too cool also. And your #6 is 190F. If that's correct, I would be trying to figure out what's wrong with that cylinder.
 
hey carlos, while I don't know your specific engine per-se, basing it on general engine operations, I still believe the readings are not accurate. Your oil temperature is too low. Even if it is the real temperature, it needs to be higher (to get rid of the moisture because that will be a rust catalyst if it is on the ground).
Your CHT's look real nice, but for the power setting you have as @Ducs mentioned also doesn't reflect a true reality. I would expect a minimum of 340-360CHT which is a rather nice and recommend operating temperature for your engine.
While EGT absolute numbers are not something to concentrate on, the actual values look reasonable, albeit maybe 50-100 lower of what I would normally see.
Factoring in your OAT, it is definitely a bit off scale.

If you have a infrared temperature gauge, after a flight and on shutdown, I would record the temp reads and probe each cyl head to see if it is close to matching.
are your CHT probes the ring type ones over the spark or some different kind? if so are the plugs torque'd correctly?

ps your cyl 1 and 3 are "in the red box", they are not lean enough. With the 23 square from your pic I would definitely like to see 350 plus CHT's.
If unleaned in this configuration it would yield about 60-65% HP

is your engine running rough or smooth? because you have a large spread there in the EGT differences, -80 vs -6.

to explain my rationale: when you're leaning, not all cylinders peak at the same time, so you're pulling the the cyls on the left side of the peak EGT and the richest needs to be ideally -25 or more. When there is a large spread, say one cyl at -25 and one at -100, that -100 one is running much leaner not able to produce as much power as the other cyl's and therefore creates roughness, this is more noticable at 4 cyl engines for 6 cyl (1 out of 4 vs 1 out 6).
When you lean and are in the redbox so to speak, a cylinder there would exert a higher CHT. Now looking at cyl2 and 3, they are very close CHT wise, but cyl2 is your leanest, I would expect this one to have a lower CHT, and cyl3 because it is the richest and in that redbox, incurring more ICP (internal cyl pressure) it to read a higher CHT, but it is one of the cooler ones.

I am trying to say that the readings are going against the laws of physics so I question the readings, it troubles me that after the oilT sensor replacement you start to see different readings already.

I would not let go on this and use infrared gauges, while the engine is running stationary or so, and check the temps and the readings.

Do you have specs for the probes, which ones they are?

ps I don't mean to make you worry or freak you out, but some of the readings just don't line up. I had similar thing in my 4 cyl engine where CHT2 is the hottest, that does NOT make sense. That's the one front where most of the airflow is, it should be one of the coolest and sure enough, detected miswire 2 and 4 were swapped. $ is the one that receives the least airflow hence always being hotter. Had a whole write up on sensors, reading and normality from personal experience here if you like to read here
xander
 
Carlos MV said:
i closed the cowlings and wen to the air to find the same old (Even worse). My oil temperature was again below 120* all through the flight Including the climb.
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I know this has been mentioned, but I'd believe the "below 120" if it was Celsius.
 
To update you all on this subject, the shop, after checking everything installed and having spoken with Garmin about my aircraft situation, they ordered a new GEA 24 unit from Garmin and exchanged the previous one but nothing changed. The readings were still faulty. They are now consulting with Garmin once again to see what could be the next steps.
 
Carlos MV said:
To update you all on this subject, the shop, after checking everything installed and having spoken with Garmin about my aircraft situation, they ordered a new GEA 24 unit from Garmin and exchanged the previous one but nothing changed. The readings were still faulty. They are now consulting with Garmin once again to see what could be the next steps.
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thank you for the update carlos, yeah keep us posted, I am very interested to learn what the culprit of this all is, as the system doesn't seem to give you accurate info. Ps were the (temp) probes also reviewed? I'd almost want to take them out while connected into a cup of warm water or so of known temperature and see what it says?
xander
 
There seems to be a clue in that with the cowl off, the temps got to around 172 F after a brief ground run at moderate power. Is there any chance the cowl is rubbing or shorting something in the system and/or introducing stray currents somehow? I think these new systems require a "clean" signal and possibly the cowl is somehow changing that.

I lost a cylinder once due to a clogged injector, and it still read about 160 F from conducted heat. So if the cylinder reading 190 CHT is in fact working the system is simply not correct. Second the IR thermometer all around and compare with panel.
 
xander75 said:
thank you for the update carlos, yeah keep us posted, I am very interested to learn what the culprit of this all is, as the system doesn't seem to give you accurate info. Ps were the (temp) probes also reviewed? I'd almost want to take them out while connected into a cup of warm water or so of known temperature and see what it says?
xander
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I have. New info but we have yet to find the cause of the problem. Seems like it is not any of the new Garmin components but some type of interference.
 
Steamflyer said:
There seems to be a clue in that with the cowl off, the temps got to around 172 F after a brief ground run at moderate power. Is there any chance the cowl is rubbing or shorting something in the system and/or introducing stray currents somehow? I think these new systems require a "clean" signal and possibly the cowl is somehow changing that.
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We have finally determined that the erroneous temp indictions happen only when the cowls are on. Even when only the lower cowl is on, temperature readings from oil temp and most fwd CHTs drop extremely. When running the aircraft without cowls then the temp indications are more realistic. An interesting thing is that the changes aren’t immediate but they happen gradually after removing/placing the cowls; they take a few minutes to adjust up or down.
Either the cowls have something to do directly or, indirectly, they are retaining some signal within the engine compartment that is causing the interference on the temperature readings.
Full troubleshooting has been done hand in hand with Garmin Until now. GEA24 and temperature sensors were replaced by them as part of the troubleshooting. I can affirm that the new Garmin system is working fine and it is not defective, however, I’m somewhat disappointed that they have now called off all assistance as they say this is an “airframe issue”.
Any help and expertise is greatly appreciated.
 
What temperature are all your thermocouples (CHT, EGT, Oil T, OAT) reading when the engine has been sitting overnight, cowl on and cowl off? They should all read close to ambient.

Did you replace all of the JPI thermocouple wires with the new Garmin install? If not, are the new Garmin probes compatible with your old JPI wiring? (I believe they are both K type, yellow & red wires).

The only other thing I can think about is grounding. Should be fresh wire, new connector, clean bolt/washer/mounting face, and to the engine block (not accessory case, not air frame, not engine mount). At least to my knowledge.

I’m not an A&P.
 
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455 Bravo Uniform said:
What temperature are all your thermocouples (CHT, EGT, Oil T, OAT) reading when the engine has been sitting overnight, cowl on and cowl off? They should all read close to ambient.

Did you replace all of the JPI thermocouple wires with the new Garmin install? If not, are the new Garmin probes compatible with your old JPI wiring? (I believe they are both K type, yellow & red wires).

The only other thing I can think about is grounding. Should be fresh wire, new connector, clean bolt/washer/mounting face, and to the engine block (not accessory case, not air frame, not engine mount). At least to my knowledge.

I’m not an A&P.
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Thanks for your reply,
Overnight my CHTs, EGTs, OilT and OAT all read actual ambient regardless if with or without cowls.
Yes, all wiring was replaced with new ones.
The grounding directly to the engine is the one thing I will check for on monday as well as the live power source for the GEA.
I will keep you posted.
 
Since your issue is very mysterious, as a developer I would like to know the precise reason why. We used to send folks on site to work with you to understand. Some avionics vendors do still that. Now I don't know if garmin is willing enough, but I would definitely raise that question to see if they have a local rep or so that can check with you on your plane for some reasons and do some verifications. I am starting to believe, and no proof for that, that your sensors are very sensitive to enclosure. Maybe if you have something like a lopresti cowling it throws these sensors off or so. And that is a hw issue that the vendor has to understand and absorb. If at all you are doing them a favor helping them shape their product to be more compatible...!
 
I had a similar low oil temp with my GO-300, with the Cessna gauge reading below the green arc.
I bought a digital temp meter and some 9 ft type J thermocouples. I bonded one to the inlet and outlet of the oil cooler.
At 75% power cruise the temps got to 108 degF. !
After replacing the vernatherm and removing the oil cooler to inspect for restrictions....no change.
I now tape over 1/2 to 3/4 of the cooler to get the oil temps to 160-180 degF, depending on the OAT.
During the 100 deg days here , I still have to cover 3 of the 10 sets of fins, and at 50 degF I cover 7 of 10 sets.
 
There are alternate OT sensor ports on the front of the engine. Install an inexpensive gauge and sensor to get a basis of comparison.
 
This is an interesting problem. Temp trends with and without cowl are inverse to what’s expected. I doubt the cowl has anything to do with it but the inverse trending probably does. I’d get a different installer who’s familiar with the G3X to go through the installation and wire terminations. Chances are high that it’s an installation problem.
 
JimH in CA said:
I had a similar low oil temp with my GO-300, with the Cessna gauge reading below the green arc.
I bought a digital temp meter and some 9 ft type J thermocouples. I bonded one to the inlet and outlet of the oil cooler.
At 75% power cruise the temps got to 108 degF. !
After replacing the vernatherm and removing the oil cooler to inspect for restrictions....no change.
I now tape over 1/2 to 3/4 of the cooler to get the oil temps to 160-180 degF, depending on the OAT.
During the 100 deg days here , I still have to cover 3 of the 10 sets of fins, and at 50 degF I cover 7 of 10 sets.
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That is not ok and if I was you I would keep troubleshooting either the sensor or the gauge. Realistically no engine at 75% power can run at 108º if you think about it.
Be careful, you can damage the engine.
 
Gentlemen,
MY problem has been finally resolved.
To make a very long and painful experience short in writing, the problem was the wire used for the harnesses. The shop used very high quality wires but for some reason these were causing some interference. They finally re-made the harnesses with the more "simple" yellow JPI type K wire and "voila", all CHT temperatures were reading fine. There was also an issue with the connection of the oil temperature probe and a damaged manifold pressure sensor.

Definitely there was the Installers fault in the way they nailed the troubleshooting. I always know that this had to do with something in the installation but they were certain that it wasn't their work; they were very stubborn. My frustration is that even though Garmin was involved in the troubleshooting all the way, this issue passed by them inadvertently. I feel Garmin's customer Service was horrible and their tech support very deficient. Hard to believe when it comes to such a great company but I guess now this is the norm and we all have to get used to this poor quality of service.
 
Carlos MV said:
Gentlemen,
MY problem has been finally resolved.
To make a very long and painful experience short in writing, the problem was the wire used for the harnesses. The shop used very high quality wires but for some reason these were causing some interference. They finally re-made the harnesses with the more "simple" yellow JPI type K wire and "voila", all CHT temperatures were reading fine. There was also an issue with the connection of the oil temperature probe and a damaged manifold pressure sensor.

Definitely there was the Installers fault in the way they nailed the troubleshooting. I always know that this had to do with something in the installation but they were certain that it wasn't their work; they were very stubborn. My frustration is that even though Garmin was involved in the troubleshooting all the way, this issue passed by them inadvertently. I feel Garmin's customer Service was horrible and their tech support very deficient. Hard to believe when it comes to such a great company but I guess now this is the norm and we all have to get used to this poor quality of service.
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Especially since Garmin deliberately restricts the sale of their products to approved installers to avoid such issues. Whereas people like me, with zero experience, can install a JPI or EI engine monitor and have it work flawlessly.
 
Garmin is VERY specific about the wire required for installation, and it’s very expensive. I remember it well. That the installer tried to cheap it out and their action created problems isn’t Garmin’s fault or problem. Criticizing them for the installer’s mistakes is misguided. The G3X support I’ve received is absolutely top notch.
 
Stewartb said:
Garmin is VERY specific about the wire required for installation, and it’s very expensive. I remember it well. That the installer tried to cheap it out and their action created problems isn’t Garmin’s fault or problem. Criticizing them for the installer’s mistakes is misguided. The G3X support I’ve received is absolutely top notch.
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I'm sorry to differ from your opinion but their very specific and expensive wire was the problem in my case. As a matter of fact, a cheaper but more reliable wiring was the one that worked for me, so yes, it is Garmin's fault that they aren't even open to consider other wirings.
I do agree it is an installer's mistake but Garmin chooses who I can install with in my region. I contacted Garmin several times to discuss my opinion on the installation made by their authorized dealer and they were very clear to me that they couldn't discuss with me any information or share information directly to me; that I had to deal with it through the dealer directly and the dealer was the one who would decide if he wanted me in the discussion (which he didn't).
It is Garmin's fault that they don't train their dealers or supports them adequately. It is even ridiculous that I purchase and pay for this system but they don't let me get involved in my own system troubleshooting. If they would have listened to me in the first place we could have saved easy two or three months of problems.
 
Stewartb said:
This is an interesting problem. Temp trends with and without cowl are inverse to what’s expected. I doubt the cowl has anything to do with it but the inverse trending probably does. I’d get a different installer who’s familiar with the G3X to go through the installation and wire terminations. Chances are high that it’s an installation problem.
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It has finally been resolved and yes, it was an installation issue probably due to lack of experience (I was the first G·X ever installed by this shop) but also lack of adequate support by Garmin. 4 months to solve this. To this day I still wonder if the shop really used the materials that Garmin recommends as they say but Garmin is unwilling to share any information on my aircraft installation experience with me.
I think it is unacceptable but it is what it is at this point.
 
Your shop is telling you stories. Garmin has had huge success with the G3X and your story is unique. I followed the manual and mine works great. Anyone who’s installed one would have recognized the wire deviation very quickly.
 
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