Low oil Temperature

[Guest]

I'm having issues with a J model which has low oil temperature.  We installed a newly overhauled engine last summer with all new baffle tapes, sealed every conceivable gap in the metal baffle tapes, all engine accessories were overhauled.  The engine is operated at normal cruise power setting with CHT values of 300+/- and the oil temps on the G4 between 125-150.

Lycoming say it sounds normal for OAT in the 20's to 30's and suggested a call to Weber Aircraft, who were equally stumped.

Any ideas?

Clarence

[gsengle]

Just that it doesn't sound normal to me... my Lyc had no trouble hitting 170-180 even in bitter cold weather at altitude...


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[Andy95W]

Clarence, I think people are reluctant to post because if you're stumped, then everyone else is probably even more baffled.

I'll try:

1.) Thermocouple test for accuracy?

2.) I thought there were multiple places to take oil temperature on the Lycoming, to allow factory and aftermarket non-certified oil temp gauges to be installed at the same time.  I've heard the forward location tends to show a lower temperature (I could be wrong about this)

If the thermocouple tests correctly, I think I would block off half of the oil cooler and test fly. It may be possible that you actually sealed up the baffling so well that 150° is the best you'll see until the ambient temperatures rise.  (If this is the case, you'll likely get a bunch of customers to refurb their baffling.)

[Shadrach]

That is only slightly cooler than where mine runs at those temps.  Freezing OAT means I'm looking at 165ish unless I winterize the cooler.

[201er]

After I had the oil cooler overhauled, I was having a hard time getting the oil up to running temp on the ground. This wasn't for very long. Oil cooler performance starts to degrade and summer is around the corner.

[PTK]

With CHT around 300 and OAT 20 to 30 and having sealed the engine really well, it sounds to me the whole engine itself is running cool and just not getting hot. And if the whole engine is running cool the oil is not going to get hot either. 

Warning! I'm not an A&P.  I'm only a pilot. But I do like to start with the simple things and not overlook the obvious. Therefore this is my observation based on the data presented!

[Awful_Charlie]

Is there not a thermostat for the oil cooler circuit in this model? I'm pretty sure there is on mine (the vernatherm), and it bypasses the oil cooler until ~160 or so

[M20F]

Have you tried covering the oil cooler and seeing if that changes the temp?  Would at least help to pin point the issue.  Sounds to me like a probe issue. 

[carusoam]

Summarizing what I think I read...

1) cool OATs help keep the engine cool.

2) cool engines don't heat the oil as much.

3) vernatherms don't open until they are sitting in hot oil.

4) vernatherms don't completely block oil flow to the oil cooler.

5) the test for vernatherms is a pot of boiling water.

6) TC location can provide some difference in temperature.  

7) proving the TC to be working is a good idea.

8) a general and easy way to see if the TC is working... check it's reading before engine start. CHTs, EGTs, and oilTs tend to be reading similar to the OAT.

9) the real way to test the accuracy over a wide range of temps. Is the ice pail and boiling water method... but this requires removing the TC from the engine...

10) the reason why people use the winter blocking mechanism for the oil cooler is to maintain better flow through the device.  Stagnation of oil in the cooler can lead to its blockage in flight.  Blockage can cause an overheat situation later...

PP collecting information, not original ideas...

Best regards,

-a-

[Guest]

Yes this engine has an oil vernatherm valve, which was replaced with the engine overhaul.  Another was installed just the other day.  The oil cooler does not get hot, which suggests no flow to the cooler as the vernatherm is not hot enough to close.

Also taped over have of the cooler face, with no real change in oil temperature on the following flight, we're reluctant to tape over fully.

It appears that the engine simply does not get warm enough to need oil cooling.

Clarence

[Brian Scranton]

Dumb question--but is it possible its reporting oil temps in Celsius? 

[M20F]

1 hour ago, M20Doc said:

It appears that the engine simply does not get warm enough to need oil cooling.

What happens when you fly around, heat it up, and then run it on the ground tail to the wind?  The oil temp should start to go up at some point.

[wishboneash]

19 hours ago, Brian Scranton said:

Dumb question--but is it possible its reporting oil temps in Celsius? 

That would be dangerously hot for oil T (approx 250-300F).

[Brian Scranton]

On March 24, 2017 at 0:39 PM, wishboneash said:

That would be dangerously hot for oil T (approx 250-300F).

Like I said...dumb question! 

[carusoam]

Oil has a degradation temperature around 350°F.  As in, it starts to degrade above this temp.  It will degrade faster above this temp... degradation signs are loss of viscosity and or carbon build up...

The OilT sensor might not be seeing the hottest places the oil actually sees.  The oil up around the exhaust valve gets even hotter...

PP thoughts only, not a mechanic...

Best regards,

-a-

Edited March 26, 2017 by carusoam

[Smiles201]

In the category of WAG: Oil not circulating properly? Try lighter weight oil? Open up the dog house to decrease cooling?

[mooniac15u]

3 hours ago, Smiles201 said:

In the category of WAG: Oil not circulating properly? Try lighter weight oil? Open up the dog house to decrease cooling?

No doghouse on the M20J. 

[carusoam]

In the case of the dog house... How does one open up the dog house?

How does that work?

I probably am missing something... 

Best regards,

-a-

[N201MKTurbo]

Seeing that it's a new engine, I wonder if there is something wrong with the piston oil nozzles. If they weren't working that would account for a lot of oil that is not being heated by the pistons. I don't know what could block all four or how to test the theory without taking them out. 

[tony]

Clarence,  did you put the temp probe in a pot of water and heat it up comparing the temps to a thermometer to make sure its reading correctly? 

 

 

[Guest]

I'm awaiting the return of the plane to do further digging at the next oil change.

Clarence

[mike_elliott]

On 3/23/2017 at 6:53 PM, Brian Scranton said:

Dumb question--but is it possible its reporting oil temps in Celsius? 

good point, we all know a Canadian Deg F is worth less than a US Deg F.

 

[Guest]

5 hours ago, mike_elliott said:

good point, we all know a Canadian Deg F is worth less than a US Deg F.

 

Yes but we get more of them, more often.

Clarence

[THill182]

I had a similar problem with my IO550G (Ovation) after an overhaul that included a new oil cooler. The overhaul was done extremely well I think, and the engine ran without any vibration at all (compared to what it was before anyway_. In the winter, even at moderately cold temps only, Oil temps would go into the yellow range (below 170F), and even below 160. Ultimately and after checking everything (replacing valve that is supposed to regulate this), the mechanic opined that perhaps the engine is just running cold because of little friction -- all parts are very well fitted. Anyway, at some point I just accepted that this is how it works, and I now use aluminum tape on the oil cooler in the winter, eventually covering about 75% of the surface when it's cold. The bonus is that in the summer when it is really hot I remove all aluminum tape from the oil cooler, and the engine remains nicely cool (185F to 190F).

[takair]

On 3/22/2017 at 7:34 PM, M20Doc said:

I'm having issues with a J model which has low oil temperature.  We installed a newly overhauled engine last summer with all new baffle tapes, sealed every conceivable gap in the metal baffle tapes, all engine accessories were overhauled.  The engine is operated at normal cruise power setting with CHT values of 300+/- and the oil temps on the G4 between 125-150.

Lycoming say it sounds normal for OAT in the 20's to 30's and suggested a call to Weber Aircraft, who were equally stumped.

Any ideas?

Clarence

Clarence

Did you ever solve this?  I have been noticing that my oil temp has been drifting lower.  It used to hold 180f, but now tends toward 160.  Today, with about 45f OAT, it would drift between about 155 and 170.  Wonder if I have a sticky vernatherm?