Citabria High Oil Temps

E

ehaecker

Well-known member
Joined
May 2, 2022
Messages
115
Location
Memphis, TN
Hi all.

I've got a new (to me) 7KCAB equipped with a Pacific Cooler oil cooler. I've been noticing lately that my oil temp will frequently reach 210-220, sometimes as high as 235 while in an extended climb. This strikes me as abnormal for an IO-320 equipped with an oil cooler. Do these numbers sound reasonable? I'm no mechanic, but I had a couple thoughts:

-Bad or stuck Vernatherm (don't know if this aircraft even has one)

-Oil filter clogged or otherwise not flowing properly

I'm really hoping to avoid the dreaded "send it off" solution and be grounded right at the beginning of the flying season. Anything I can do to troubleshoot or solve the issue locally and same day or weekend would be great.

The cooler is fairly new, Replaced in August 2019. I'll mention it to my IA next time I talk to him, but I wanted to throw it out to the forums in the mean time. Any ideas or suggestions?

Thanks!
Eric
 
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Could be a bad vernatherm, can be tested with heat and getting a measurement, but more often than not it’s a dirty oil cooler, bad baffling, exc. Seen someone put tape over as a winter cover and never was removed. All that good, go to the vernathearm. Wouldn’t think the cooler would be the problem being that new.
 
Bob Turner said:
Make sure your baffles are up and forward?
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Definitely a good suggestion. I did have the cowl off yesterday. Baffles are now for sure correct (didn’t think to check before removing it). Might do a test flight to see if there’s any change.
 
Hammersmith said:
Could be a bad vernatherm, can be tested with heat and getting a measurement, but more often than not it’s a dirty oil cooler, bad baffling, exc. Seen someone put tape over as a winter cover and never was removed. All that good, go to the vernathearm. Wouldn’t think the cooler would be the problem being that new.
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I’d sure hope the cooler isn’t the problem. That said, the airplane had sat for a long time prior to my purchase. Previous owner lost his medical and couldn’t fly it. It’s only flown a handful of times in the last 3 years and was mostly taxied and ground run. So I wonder if there’s some “gunk” built up in the cooler from all the inactivity.
 
ehaecker said:
I’d sure hope the cooler isn’t the problem. That said, the airplane had sat for a long time prior to my purchase. Previous owner lost his medical and couldn’t fly it. It’s only flown a handful of times in the last 3 years and was mostly taxied and ground run. So I wonder if there’s some “gunk” built up in the cooler from all the inactivity.
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Lots of people go for the cooler first when it’s actually the vernathearm. If it was recently replaced it was probably due to trying to fix high oil temps the first time. Could always flush the cooler but the heat sensitive spring does go bad.
 
Hammersmith said:
Lots of people go for the cooler first when it’s actually the vernathearm. If it was recently replaced it was probably due to trying to fix high oil temps the first time. Could always flush the cooler but the heat sensitive spring does go bad.
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Yep I think you’re onto something there.
 
Well I went ahead and ordered a new Vernatherm. I’ve got to do an oil change soon anyway so that’ll be a good time to eliminate that factor.
 
another thing worth checking is the calibration of the oil temp sender and gauge. the numbers you quoted are within the green arc, no? if the calibration is off by five or ten degrees you're still in the normal range for the engine and there might not be anything wrong. drop the sender in a pot of boiling water with a thermometer and see if the gauge is close to what the thermometer is reading.
 
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Very true, and yes, still within the green. The previous owner said he's never seen it above 180-190 which tells me that either A.) He's full of it, or B.) The Venatherm has decided its duties are over.
 
ehaecker said:
Very true, and yes, still within the green. The previous owner said he's never seen it above 180-190 which tells me that either A.) He's full of it, or B.) The Venatherm has decided its duties are over.
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what was the outside air temp when you experienced the elevated oil temp and at what speed were you climbing?
 
Bartman said:
what was the outside air temp when you experienced the elevated oil temp and at what speed were you climbing?
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It varies, but most recently it was maybe 75-80 F, climbing around 80 MIAS. On cooler days with less climbing it will still reach 210-220 pretty easily. Certainly not feeling great about it with the hot Memphis summer coming up. The new Vernatherm should be an easy swap while doing my oil change. Might even pull the cooler while I'm under the cowl and just verify there are no obstructions like bugs and any other junk.

My old PA-16 (recently sold to a good buddy) has an O-235 on it with no oil cooler, and these temps are very typical for it. 230 or so in the middle of the summer is the hottest I've ever seen it.
 
Download a copy of Lycoming Service Instruction SI1316a
prior to replacing the vernatherm...
More often than not the sealing surface of the seat is conforming to the surface of the pintle (it doesn't have a rotater) and without doing a lap job on that seat your new vernatherm will make the bypass problem worse, not better.

Chris
 
ehaecker said:
I believe 180-210 is what Lycoming says to be ideal.
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I'm searching the Lycoming site but all I can find is this in an article about cold weather ops
The desired oil temperature range for Lycoming engines is from 165˚ to 220˚ F.
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Operating in Cold Weather

A note that came in the mail from a Flyer reader included a suggestion that went something like this, “How about an article dealing more extensively with the cold-start problem?” This suggestion was a good one as it provided an opportunity to share information about a variety of cold-weather...
www.lycoming.com www.lycoming.com

The thing is, if you're not sure what's going on inside your engine the first thing you have to know is whether or not your gauge is accurate. Your temperature isn't wildly out of line so it's possible it's still within normal and there's error in the gauge. It's easy enough to check and might be all you need to do to know what's happening in the engine.

Lycoming seems to defer to airframe manufacturers for what is correct in terms of normal and maximum oil temps, you'd think there'd be guidance but the cold weather ops article is the only one that has anything.

An 8KCAB POH I'm looking at says the green arc is 100 to 245, fwiw.
 
Hiperbiper said:
Download a copy of Lycoming Service Instruction SI1316a
prior to replacing the vernatherm...
More often than not the sealing surface of the seat is conforming to the surface of the pintle (it doesn't have a rotater) and without doing a lap job on that seat your new vernatherm will make the bypass problem worse, not better.

Chris
Click to expand...
Going through the Lycoming site, there are a lot of articles in the Knowledge Base that seem like worthwhile reading for owner/operators!

Knowledge Base

www.lycoming.com www.lycoming.com
 
ehaecker said:
It varies, but most recently it was maybe 75-80 F, climbing around 80 MIAS. On cooler days with less climbing it will still reach 210-220 pretty easily. Certainly not feeling great about it with the hot Memphis summer coming up. The new Vernatherm should be an easy swap while doing my oil change. Might even pull the cooler while I'm under the cowl and just verify there are no obstructions like bugs and any other junk.

My old PA-16 (recently sold to a good buddy) has an O-235 on it with no oil cooler, and these temps are very typical for it. 230 or so in the middle of the summer is the hottest I've ever seen it.
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What did the temp do when you got to altitude and accelerated? Did it stay high or come down to a more comfortable level?
 
Bartman said:
What did the temp do when you got to altitude and accelerated? Did it stay high or come down to a more comfortable level?
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It did eventually come down and settle around 220, but that was with the power pulled way back. Like “low and slow lazy flying” setting instead of “I’m tying to go somewhere setting”. I want to say I had it back to 2100-2200 or so.
 
hmmm, i see why you think you've got a problem somewhere. good luck getting it worked out. i'd be surprised if it was the oil cooler but weird stuff happens in airplanes so anything's possible. vernatherms's aren't bullet proof, so good luck swapping it out.
 
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