High oil temp question

A

asgcpa

En-Route
Joined
Jul 19, 2012
Messages
2,559
Location
Illinois
Display Name
Display name:
CPA
Am in Indy for a tax seminar. Went to a local airport, hired a CFI and rented a 182 for some night flying. Had to wait a bit for oil temp to come up into green prior to take off. By the 4th circuit, oil temp went through the roof. There were 8 qts of oil. CFI said it was ok. Suggestions why this happened? We had to cut the flight short.....
 
asgcpa said:
Am in Indy for a tax seminar. Went to a local airport, hired a CFI and rented a 182 for some night flying. Had to wait a bit for oil temp to come up into green prior to take off. By the 4th circuit, oil temp went through the roof. There were 8 qts of oil. CFI said it was ok. Suggestions why this happened? We had to cut the flight short.....
Click to expand...

The oil cooler has a thermostat, the Vernatherm, which can be clogged with carbon as can the cooler itself. The cooler could have also had an external blockage. Did you look at it?
 
Did it smell hot? My 182 if you get it up toward the upper end of the gauge, it will smell hot. If not, I'd suspect the gauge. Also it will climb on a hot day up toward that end doing crash and dash, if you don't leave the cowl flaps open. But at night, this time of year? If it's truly getting that hot, something's wrong.
 
Vernatherm or oil cooler are the most likely options to me.
 
asgcpa said:
As high up on the gauge as you could go.
Click to expand...

Interesting. As others have said, something is probably plugged. Or, it could be the gauge itself.

As an aside, mine runs at least 15 degrees warmer if I'm running a multi weight.
 
For a rental, or in flight, assume the plane is broke.

For an owner trying to troubleshoot, always start with the gauge. More often the gauge is wrong. We just chased a high oil pressure reading.
1- Applied regulated pressure to the panel gauge, the gauge reads dead on what the regulated pressure was.
2- Put a certified external gauge directly on the engine, the oil pressure read exactly on spec (lower than the panel gauge said.)
3- Put the external gauge inline between the engine and panel gauge, the external gauge read exactly as (2), and the panel gauge read high exactly as before.
What's more, it reads exactly 10 Psi high across the entire range, as you increase and decrease rpm.

So the panel gauge reads 10 psi high, but only when actually connected to the engine. A&P is scratching his head on that one.
 
90% chance the engine is improperly grounded to the airframe. The alternator current tries to find other paths when the grounding has even a fraction of an ohm's resistance, and one of those paths is through the electric temp sensor. The alternator's current boosts the sender's current a tiny bit and the gauge goes nuts.

Cessna came out with a retroactive fix: a ground wire directly from the engine case to the gauge case. But the engine grounding still needs looking at.

Dan
 
In any event, abide by the following motto: "If it ain't broke, don't fix it, but if it ain't fixed, don't fly it." If the oil temp pegs high, something is broke, and you should land appropriately soon rather than continue the flight for long. If there are no other indications of oil system problems (e.g., losing oil pressure), it's probably not worth landing in some farmer's field, but if it was right after takeoff for 3-hour XC flight, I'd turn around and land even without other indications. Since you were in the traffic pattern, my recommendation would have been to make the next a full stop and let maintenance have the plane when they come to work tomorrow morning.
 
Ron, that's what we did when I noticed it doing my checks on downwind.
 
timwinters said:
As an aside, mine runs at least 15 degrees warmer if I'm running a multi weight.
Click to expand...
Is that common? I just switched from straight 50w to 10w40 for the winter (due to hard starting on cold mornings). I haven't had it up yet witht he new oil. I generally run right around 200 but have seen it as high as 210. Should I not panic if I now see 225?
 
JOhnH said:
Is that common? I just switched from straight 50w to 10w40 for the winter (due to hard starting on cold mornings). I haven't had it up yet witht he new oil. I generally run right around 200 but have seen it as high as 210. Should I not panic if I now see 225?
Click to expand...

No, if you see a stable 225 as a peak power transient, I would be okay with that, it's within spec.

It also gets it above boiling.
 
JOhnH said:
Is that common? I just switched from straight 50w to 10w40 for the winter (due to hard starting on cold mornings). I haven't had it up yet witht he new oil. I generally run right around 200 but have seen it as high as 210. Should I not panic if I now see 225?
Click to expand...

245 is redline.

I found a good temperature drop when I went to Aeroshell 15W50 from straight-weight oil.

Dan
 
Dan Thomas said:
245 is redline.

I found a good temperature drop when I went to Aeroshell 15W50 from straight-weight oil.

Dan
Click to expand...
Actually, I think it's 240*. But some older O470's, like mine, have a 225* redline.

Also, many times the oil temp probe is located at the coolest spot in the system. Thus, if you're reading 240 then the "working oil" temp could be above 260 or even 270. Not good for the oil.

My experience with multi-grade has always been with Phillips 20/50 XC and my engine oil temps will be substantially higher running it than when I'm running straight weight Shell. In fact, if I put a couple of "make-up quarts" of 20/50 into 8 qts of straight weight and the effect will be the same.

In my case, though, it's not an issue since I struggle with the oil staying too cool, not getting too hot.
 
Last edited:
JOhnH said:
Is that common? I just switched from straight 50w to 10w40 for the winter (due to hard starting on cold mornings). I haven't had it up yet witht he new oil. I generally run right around 200 but have seen it as high as 210. Should I not panic if I now see 225?
Click to expand...

Sorry about the thread drift;
But we did a little XC this weekend with the new oil (it was actually 20w50, not 10w40 as I said previously). Rather than our usual 200-205 degrees with straight 50w (Aeroshell 100 plus), we saw a drop to around 185 the whole trip. I think I would have been happier with an increase. Of course, it was cold (mid 50s) outside but that doesn't usually effect my oil temp in cruise. But it did start a easier with the multi-grade.
 
timwinters said:
Also, many times the oil temp probe is located at the coolest spot in the system. Thus, if you're reading 240 then the "working oil" temp could be above 260 or even 270. Not good for the oil.
Click to expand...

That's right. The oil temp is measured at the entrance to the system, after it's been through the cooler.

lycacccaseoilschematic.jpg


Dan
 
Dan Thomas said:
That's right. The oil temp is measured at the entrance to the system, after it's been through the cooler.

lycacccaseoilschematic.jpg


Dan
Click to expand...

is that the same for aftermarket systems, also? I've got a UBG-16, and the alarm is set at 210. I didn't know how the sensor location compared to the factory setup on my mooney.
 
You must log in or register to reply here.
Back
Top