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Unusual Oil temp

Bavafa

Well Known Member
I went for a flight yesterday which I experienced a very unusual oil temp for my plane. My temp has been steady between 180-200 depending on the season and OAT for this time of the year, 180-185 would be a normal temp.

Last week I was flying (short duration) and I saw suddenly a very high oil temp as I added some power to climb. Surprised by the high oil temp, I pull the power and the temp came down right away. I richened the mixture a bit and from there on, it looked normal.

Yesterday I went for another flight and as I took off, within a minute or so I saw my oil temp at 238, I immediately reduced power and decide to go back and land. As I pulled the power (reduced manifold) my oil temp immediately started coming down and when I added power to get into the pattern altitude, the oil temp would immediately go up. So I tried this two or three times more and the behavior was near instant as if the oil temp was controlled by the black knob. I landed and went back to the hanger to look things over. Took the cowl off and did not find anything abnormal. During the high oil temp, my oil pressure was unchanged at all, right around 77 PSI.
I made three separate flight after and all normal temp and could not get it to replicate.

The only change that I can think of is that I had updated my Garmin data base during the time this behavior had shown itself and I was wondering if the data base update could cause issue a bug in the OS to show itself?

My question is
- Has anyone else experience this
- Is it possible that this is an actual and true oil temp that is being reported? Could oil temp go up so quickly and go down so quickly.
- Could this be a probe issue? Again I am puzzled that it would be effected by the manifold pressure
- Could data base update cause a bug in the OS (I guess this is more of question for advanced users)

My avionics are all Garmin G3X and I am on version is 8.60
 
The speed of the change, and the fact that the pressure didn't change, are both pointing to an instrumentation error of some type.

First - you can't change the temperature of that much oil quickly - it will take 4-5 minutes to make it swing by 30 degrees, either way.

Second - if the temperature goes up that much, the viscosity will drop and the pressure will go down, and you didn't see that happen.
 
Adding to airguy's response, did CHTs also go up? (guessing not, since you didn't mention it). Agree, it is an erroneous reading. Look first for a weak/poor ground.
 
The speed of the change, and the fact that the pressure didn't change, are both pointing to an instrumentation error of some type.

First - you can't change the temperature of that much oil quickly - it will take 4-5 minutes to make it swing by 30 degrees, either way.

Second - if the temperature goes up that much, the viscosity will drop and the pressure will go down, and you didn't see that happen.

+1

oil temp simply doesn't change as rapidly as you are seeing here. You want to correlate the power change back to your instrument change. Most likely aer either an electrical issue with alternator/VR (changes in alt RPM create electrical changes) or a mechanical issue where vibration or physical movement of engine is creating a wiring (i.e. resistance) issue. THe fact that no other instruments issues are seen, points to the latter.

Larry
 
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Oil Temp Wire Connection

I experienced a similar issue. My oil temp starts out normal then quickly ran over 235. I remember trying lots of different things, found there was a relationship to engine power. That got me looking for a loose wire (more power, more vibration = erratic temp) I replaced the oil temp sensor connection (small wires at end of temp probe) and all was back to normal. I did not have to replace the probe, just the connection.

Might try the connection first as it pretty easy to do. Good luck.
 
I will add that I saw something similar to this in the recent past when the cooling air to my oil cooler was cut off completely (flapper valve broke). In this case any power above idle caused oil temps to rise rapidly but when I pulled power back temps would normalize. Maybe not as drastically as you saw but similar effect.
 
I agree that the oil temp does not simply go that high up and cool down so quickly so this is either a probe issue or software bug. The fact that the temp goes up and down by manifold pressure (not RPM) makes vibration less likely. Also noteworthy that it does not jump but goes up.
Here is the graph for my engine data but I don't seem to be able to post the code correctly.

I am wondering if someone can help me post this graph, I can email it or some one can help me to see how I can get the code from photo bucket or flicker. Neither site provide a code so I can post it here.

https://s1339.photobucket.com/user/mmehranp/media/Oil temp issue_zpspkdgtzg8.png.html?sort=3&o=0

https://s1339.photobucket.com/user/mmehranp/media/Oil temp issue_zpspkdgtzg8.png.html?sort=3&o=0
 
I agree that the oil temp does not simply go that high up and cool down so quickly so this is either a probe issue or software bug. The fact that the temp goes up and down by manifold pressure (not RPM) makes vibration less likely. Also noteworthy that it does not jump but goes up.
Here is the graph for my engine data but I don't seem to be able to post the code correctly.

I am wondering if someone can help me post this graph, I can email it or some one can help me to see how I can get the code from photo bucket or flicker. Neither site provide a code so I can post it here.

https://s1339.photobucket.com/user/mmehranp/media/Oil temp issue_zpspkdgtzg8.png.html?sort=3&o=0

https://s1339.photobucket.com/user/mmehranp/media/Oil temp issue_zpspkdgtzg8.png.html?sort=3&o=0

To me, chart doesn't show a correlation between MAP and oil temp. Looks like an isolated blip on oil temp. THe fact that MAP is changing at that time does not directly correlate it. Many other changes in MAP on that chart that do not correlate with OT change.

EDIT: Ok, I see a slight bump with other MAP changes. But why a huge jump on one change, but very small on the others.

I would still be looking at an electrical issue. MAP sensor changes its output voltage as MAP chnages. It is not resistive, but a transducer. I also feel that vibration will change with MAP increase, regardless of RPM. Watch a motor in a car as it rev's. As soon as the throttle goes down, the engine twists sideways (opposite from crank rotation) from the torque even before the RPMs go up. Much less pronounced if in neutral. However, the steady rise as opposed to jumping points to some electrical relationship with the MAP output vs loose connection due to vibration, though that could just be s/w smoothing in the instrument. My G3X seems to ahve a great deal of smoothing of instruments, outside the RPM and MAP.

Larry
 
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Larry,
Looks like you were able to see the graphs. I will pull the data file from the hanger today for yesterday flight which I was able to replicate the correlation of oil temp to MAP both in increase and decrease. Now whether that is a due to vibration or OS issue, that I don't know.

I have sent this info to Garmin and I am hoping to hear back from them.
 
Larry,
Looks like you were able to see the graphs. I will pull the data file from the hanger today for yesterday flight which I was able to replicate the correlation of oil temp to MAP both in increase and decrease. Now whether that is a due to vibration or OS issue, that I don't know.

I have sent this info to Garmin and I am hoping to hear back from them.

It would be easier to post a link to the Savvy site - as long as you've made it open for public viewing.
 
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