Interesting Oil Pressure Anomaly

timwinters

timwinters

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Interesting Oil Temperature Anomaly

Edit: Changed title from "oil pressure" to "oil temperature"...brain fart.

Data:

1958 C182A
O-470L with prox 1200 hours
F&M Oil Filter Adapter (pistol grip style)
Aeroshell 100W (typically)

My plane experiences higher than normal oil temps immediately following an oil change. Not after every oil change but probably after 80% of them. This is what happens:

On the initial climb out after an oil change the temps will be 20dF higher than normal. They'll run 200* to 215* when typically they'd be at 180* to 195* depending upon the OAT. Then, in cruise, the temps will settle in at about 185* or 190*, again 20* higher than typical. At some point in time during that initial flight, the issue will go away and the cruise temp will drop to 170* ish.

And once this "bubble bursts" then 185* during climb and 170* during cruise is the norm until the next oil change.

But, after my last oil change, the issue (higher than normal oil temps) hung around for about 8 hours of flight. We did my BFR late last month right after changing the oil and I didn't see less than 200dF the entire ride (it was a HOT day). It was still high during a couple of flights earlier this month, and also when we flew down to Gaston's and during my IPC. During all these flights the climb temps were 200 to 210dF and cruise temps 180 to 190dF.

Then, last Sunday when I departed Gaston's, I climbed at 100 mph all the way to 9,500' and the oil didn't even make it to 185dF...and it settled in at 165* in cruise. And it wasn't a cool day. Back to "normal".

And it'll stay there until I change my oil again.

Ideas? And not just ideas on why it hung around longer this time but why is it doing it at all?

I have my thoughts but admittedly don't know the intimate details of the inner workings of aircraft engine oil systems.

One BTW...redline is 225* and I never see this, although we came close during my BFR. We got up to 220* once.
 
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The only thing I can think of is that something is going on with the oil cooler. I couldn't tell you what, but that's the best guess. Really though..changing the oil is just dumping the sump for the most part which I can't see how that would effect the oil cooler..

Idk...wait for someone smarter to answer :)
 
I'm thinking wear on the Vernatherm face and it is not seating but letting oil drain out and not getting warmed up to divert oil to the cooler.
 
Norman said:
I'm thinking wear on the Vernatherm face and it is not seating but letting oil drain out and not getting warmed up to divert oil to the cooler.
Click to expand...

Norm, that was one of my mechanic's first suspicions also and we put in a new vernitherm about 5 years ago at annual to try to correct the issue, no change (I'd have to check my logs to confirm the exact date).

I always thought that maybe air was getting "behind" the vernitherm, a vapor lock, so to speak, was keeping if from sensing the actual oil temps and, thus, it wasn't opening.

But I have no idea if this is even possible.
 
BTW...I can't say with confidence that this engine has been doing this since OH but easily since about 200 SMOH...so for 1000 hours!!!!
 
Do you use any oil additives? Have you replaced the oil temp sender?
 
Henning said:
Do you use any oil additives? Have you replaced the oil temp sender?
Click to expand...

Camguard.

I have two of 'em, the stock one and the UBG-16. They agree.

Don't know how either one of those would come into play on a change in temps though.
 
How is your oil cooler fed? The inlet should be at the bottom with the outlet at the top. That guarantees the cooler is full of oil. Other configurations could result in an oil cooler with a bubble of air inside.
 
It's hard bolted to the case. I don't think it's possible to screw up the installation but don't know for sure.
 
timwinters said:
Camguard.

I have two of 'em, the stock one and the UBG-16. They agree.

Don't know how either one of those would come into play on a change in temps though.
Click to expand...

Change in rate of thermal exchange as the oil contaminates with lead, just as a potential guess. Since you use Cam Guard, you could try giving Ed Collins a shout, he may have an answer for you, he's the sharpest person on the subject of oil I've met.
 
On some airplanes, like the older 172s, the oil cooler is supposed to be drained at oil changes. But if you do that, air can get trapped for some time in the top of the cooler. The silly design has the outlet and inlet both halfway up the cooler, at opposite ends. It should have the inlet at the bottom and the outlet at the top.

Perhaps the O-470's ports are similarly located. Been a long time since I had one off and I don't remember. Some of those coolers had drain ports, and you should ask your mechanic if he's draining it. Might try leaving it alone next time and see what the temps do.

The vernatherm is always surrounded by oil. It's in the flow from the pump, and all it does is close off an oil cooler bypass gallery. Changing the oil would have no effect on it.

Dan
 
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