172M Oil Temps to 265!!! Help!

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WatchMeFly

Filing Flight Plan
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5094Romeo
Hello Avaitors,
I just bought my first airplane and of course I'm being hazed into the avation community with problems from the get go :))
I have a 1974 172M with a freshly overhauled engine (currently about 12 hours). I understand that I am still in the break in period and temps are going to be a bit above normal but I am experiencing oil temps of up to 265deg crusing at 4500ft at 2400rpm. Even when I baby it, I can't keep the temps below 245. I have already replace all the baffeling, oil temp probe, and brand new oversized oil cooler. The plane came with Phillips X/C but I changed it to Aeroshell 100 mineral. Any ideas???? Right now my carb heat is inoperative and the hose has been removed. Can that affect air flow to the oil cooler in some way? Also, all the avonics are brand new (dynon skyview). Is it possible something is not callibrated properly and I am getting false readings?
 
It sounds like something is very wrong! Just for anecdotal reference I can fly my O-360 C172N in 100°F weather and I only see oil temps in the 190°F range. Are you running full rich? Is your hose to your oil cooler attached? You replaced the probe, what does it connect to? Perhaps an issue with the gauge or engine monitor?

Edit: What about your vernatherm, have you looked at it?
 
The first thing I'd do is verify that the oil temperature sensor is installed in the correct location and that it is measuring accurately. If you don't know those things it will be hard to determine if you really have an oil temperature problem or not.

Assuming that you actually do have an oil temperature problem, the first thing that comes to mind is that you either have a vernatherm that doesn't work or if a vernatherm isn't installed that you don't have a viscosity valve installed. Either could have been overlooked and problematic since the overhaul 12 hours ago.
 
mondtster said:
The first thing I'd do is verify that the oil temperature sensor is installed in the correct location and that it is measuring accurately. If you don't know those things it will be hard to determine if you really have an oil temperature problem or not.
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It may be something as simple as the set up information inside the Dynon unit. I'd start there ...
 
We are working a sudden high oil temp prob on a io-520 right now and the first important observation is that before the first start of the day, the oilT is reading substantially higher that the oat probe.

As an aside, I would not fly a carb’d a/c with a deactivated carb heat.
 
I'll add that with only 12 hours on the engine, you should not be babying the engine! It won't break in properly, you risk glazing the cylinders, which means having to remove them to get rehoned.

The standard breakin procedure is to run at 70% power or more, very rich, in level flight cruise to avoid overheating. And climb at high power but shallow angles / high airspeeds to avoid overheating. Check oil before & after each flight continue this until oil consumption stabilizes, which should be about 1 qt every 15 hours, plus or minus. Of course you can get the details from Lycoming or your engine builder.
 
Poor engine grounding can do this. The alternator's ground current must reach the airframe with no resistances, and if it encounters a little bit, it starts finding other paths including through the oil temp sensor, to the gauge, and from there to the bus and battery and ground. If alternator current does that, it will jack up the temperature reading.

When you shut down after a flight, look at the oil temp. Kill the engine, shut down, then turn the master back on, with the alternator switch off, and see if the reading is the same. If it's lower, you might be fighting bad engine grounding.

The airplane is not legally airworthy with the carb heat system inoperative. I hope you're not flying like that. Even Lycomings get carb ice in the summer if the dew point is high enough, and carb ice will kill that engine.
 
mondtster said:
Assuming that you actually do have an oil temperature problem, the first thing that comes to mind is that you either have a vernatherm that doesn't work or if a vernatherm isn't installed that you don't have a viscosity valve installed. Either could have been overlooked and problematic since the overhaul 12 hours ago.
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Exactly. And this is a problem for a mechanic to sort out, too.
 
Take the vernatherm out and put it in boiling water. If it doesn't do anything it's busted. It should get shorter at 180 to 200 degrees. Before the water comes to a boil.
 
Klaus M said:
Take the vernatherm out and put it in boiling water. If it doesn't do anything it's busted. It should get shorter at 180 to 200 degrees. Before the water comes to a boil.
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It gets longer as it gets hot, not shorter.
 
Let'sgoflying! said:
We are working a sudden high oil temp prob on a io-520 right now and the first important observation is that before the first start of the day, the oilT is reading substantially higher that the oat probe.

As an aside, I would not fly a carb’d a/c with a deactivated carb heat.
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??? There is such a thing? Deactivating carb heat on a carbureted engine!?!?!? What’s the back story on that?

EDIT: just read the OP all the way through. Had just scanned through the thread at first and that deactivating carb heat in your post reached out and slapped me right upside the head. It’s inconceivable to me someone did that on purpose.
 
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WatchMeFly said:
Hello Avaitors,
I just bought my first airplane and of course I'm being hazed into the avation community with problems from the get go :))
I have a 1974 172M with a freshly overhauled engine (currently about 12 hours). I understand that I am still in the break in period and temps are going to be a bit above normal but I am experiencing oil temps of up to 265deg crusing at 4500ft at 2400rpm. Even when I baby it, I can't keep the temps below 245. I have already replace all the baffeling, oil temp probe, and brand new oversized oil cooler. The plane came with Phillips X/C but I changed it to Aeroshell 100 mineral. Any ideas???? Right now my carb heat is inoperative and the hose has been removed. Can that affect air flow to the oil cooler in some way? Also, all the avonics are brand new (dynon skyview). Is it possible something is not callibrated properly and I am getting false readings?
Click to expand...
Just saw you just joined and this was your first post. Welcome.
 
First thing I would do is to pull the oil temp probe, stick it in boiling water and see what it reads. If not 212, you have a start on figuring out the issue.
 
Where is the oil temp sensor installed? If on top of the case? Move it to the oil filter adapter and you’ll see approx 15-20° temp reduction. I’d be tempted to remove the vernitherm to see how temps change.

What’s the oil pressure? Does it drop as the temp rises?

FWIW, several years ago a friend made a flight when he knew his card heat wasn’t working. He died after engine failure (presumed carb ice) over Prince William Sound. Fix your carb heat. It’s an airworthiness item!
 
Timing?

With a carb engine 1 jug is richest and 1 jug is leanest And others are in between. Throughout the operations range of the engine you should get a slight (20?) rpm increase as the mixture is leaned. If NOT
your mixture is Too Lean. With Carb Heat ON the rise should be slightly higher.

A bud has an early 180 conversion. When new he experienced high cht problem at higher power. After swapping various p/n carb of greater richness Lycoming had him take readings and send them his carb. They set it up in a Test Cell and reamed out a jet. All was well.

Just because the baffles are new does not mean they are fitted correctly . They must fit tight so air has to flow between the fins to be cooled.

Peek inside your cowl using a cell camera if needed. The soft seals
MUST block off all paths to allow pressure to build above the engine.
You are trying to make hot air go downhill!
 
Stewartb said:
Where is the oil temp sensor installed? If on top of the case? Move it to the oil filter adapter and you’ll see approx 15-20° temp reduction. I’d be tempted to remove the vernitherm to see how temps change.
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On the O-320E2D in that 172M it's in the oil screen housing or, if there's a spin-on filter adapter, it's in that. Like all aircraft oil temperature sensors, it measures the temp of the oil as it returns from the cooler. From the O-320 TCDS:

1690045596984.png
 
Unless Dynon, like Garmin, says to install in the engine case.
 
Once again, this needs addressing:
mondtster said:
The first thing I'd do is verify that the oil temperature sensor is installed in the correct location and that it is measuring accurately. If you don't know those things it will be hard to determine if you really have an oil temperature problem or not.

Assuming that you actually do have an oil temperature problem, the first thing that comes to mind is that you either have a vernatherm that doesn't work or if a vernatherm isn't installed that you don't have a viscosity valve installed. Either could have been overlooked and problematic since the overhaul 12 hours ago.
Click to expand...
Those two things there. Make sure the temp reading is accurate. Make sure the engine doesn't have both a vernatherm and viscosity valve, and that the vernatherm is working properly.

All to be done by a certified mechanic, not the owner. This is not owner maintenance. Nor is carb heat stuff.
 
Stewartb said:
Unless Dynon, like Garmin, says to install in the engine case.
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Yes, the Continental oil temp sensor is in the case, in the gallery from the pump/filter/cooler and senses oil inlet temp, as per the TCDS for those engines.

Unless, of course, the Garmin is not STC'd to replace the OEM instruments, in which case the OEM oil temp sensor is occupying that spot and Garmin had to stick theirs somewhere else.
 
My new engine never ran hot when it was “breaking in”
It also stopped using oil at 6 hours and has been a normal engine since then for 545 hours now. I ran it at 75% power for 2 hours and then wide open power for 30 minutes first flight.
Used one qt oil.
Second flight the same only 65-75%power for 2 hours and then 30 minutes wide open throttle.
It used a half qt oil second flight. At 6 hours it was “broke in” and I flew it like normal. Don’t baby that thing.

Like said get it looked at before flying it anymore.
Got to have carburetor heat, who decided it was alright to fly without it?
 
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Do you still have the original Cessna oil temp gauge as well or just the digital? Just curious.

I may be the only one to say this, but what you’re experiencing, I don’t think I’d too far outside of normal for a M model.

I say this after lots of reading on the internet and having 2 different engines on my 76’ M model show nearly the same thing. After about 25 minutes of flying, the temps are a needle width from the redline until after landing. This was in 2 separate engines. I’ve come to accept it. The “new” engine has 1900 hours on it now operating like this.

Things I tried to correct the issue.

Changed Oil Cooler at engine swap

Tested Vernatherm

Verify Engine Baffles

Used a Hotplate on top of engine to heat 1/2 quart of oil in pan using a digital thermometer and removed sender to verify gauge accuracy by dipping in the pan while still connected. Gauge read within 5 degrees, on the high side.

Sent oil samples as well, it’s a happy engine that reads redline when ambient temp is above 75f outside.
 
In no particular order.

1. Cylinder running too lean.
2. Sufficient cooling air over cylinder.
3. Check magneto timing.
4. Check temperature probe.
 
Everyone on this feed is absolutly amazing!!!! Thank you so much for all your feedback. We are checking the vernotherm next but there are a lot of suggestions here I would have never thought of. I will try them all one by one until we get this issue fixed.
 
WatchMeFly said:
Everyone on this feed is absolutly amazing!!!! Thank you so much for all your feedback. We are checking the vernotherm next but there are a lot of suggestions here I would have never thought of. I will try them all one by one until we get this issue fixed.
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Don’t forget to write back when you find the issue, or non issue
 
Well everyone........ after extensive testing on the oil cooler, vernotherm, oil screen, baffeling, Magnito timing, oil probe,......... everything is working perfectly andI am being told by Signature that we should expect these high oil temps during break-in considering the OAT here in Texas is well over 100deg. The supposed remedy is to finish the break in flying early in the morning when the temps are down in the 80s and to "just manage the oil temps better". So, tomorrow morning at 6am I am going to attempt to get a few hours of flying in while somehow keeping the oil temps below 240. Signature told me not to worry about keeping 65% power so my plan is to get to a decent altitude and if the temps get close to 240, I'll just pull power and decend untill the temps come down.

If anyone has any other suggestions, I'd be happy to hear them :))
 
Color me skeptical. I've broken in multiple cylinders and one new engine, with and without high-compression cylinders (STC) and no matter the OAT, my oil temps have always remained rock-solid at 180F throughout. The rings should set within a few hours of break-in operation. When oil consumption stabilizes, if you are still seeing verifiably high oil temps, something is not right.
 
Have you drained the oil and inspected the oil filter? Relatively cheap to take a look. It sure seems like something isn't right...
 
chemgeek said:
Color me skeptical. I've broken in multiple cylinders and one new engine, with and without high-compression cylinders (STC) and no matter the OAT, my oil temps have always remained rock-solid at 180F throughout. The rings should set within a few hours of break-in operation. When oil consumption stabilizes, if you are still seeing verifiably high oil temps, something is not right.
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Sorry to pile on but I agree. I flew my new engine in July and it was not cool. I flew late afternoon into early evening. Mine was a zero hour lycoming rebuilt.
There was a AD for that model 172 that involved a carburetor jet which if too lean it will run hot. Did your mechanic check that? Did they check the grounds like was mentioned?

Good luck in the morning and hopefully it is not an issue.
 
Well, as I mentioned earlier…. Mine does the same thing…. At 2300 hours of doing the same thing, OAT doesn’t change too much. Is what it is…
 
Couple thoughts:

Why was the oversize cooler Installed? If a non -standard installation there

is a “possibility“ that you may have to bleed the cooler to release a trapped

air bubble that does not cool oil. Firewall mount?


Is Static RPM per spec?

Too high of a pitch might cause lower Static and higher temps.


Blow- by would be hot gases getting past the rings and heating the oil.

One way to evaluate this is plumbing a Airspeed Indicator into the breather.

I believe there is a spec on this somewhere.
 
Redline is redline.

I can’t imagine how an engine with 265° oil smells but I wouldn’t be comfortable flying it!
 
IIRC when we had the engine break-in, we were told not to fly at high altitudes, and to run her hard.
 
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