High oil temp when climbing

[Prior owner]

Thought I’d throw this into the thread-  This is the first summer that I’ve flown my Mooney, and while the oil temp has always run on the warm side (200F oil Temp in winter), when it’s 95+F OAT, my oil temp has been hovering around 220-225F during cruise and climb. Gauge checked with portable thermocouple and is very accurate...

I found this today- the wrong vernatherm is installed. It is stamped 85C. Not sure how I missed this, but I did.... I have no idea who installed it. I have ordered Lycoming Vernatherm part # 53E22144 and will post the results of a flight test here afterwards. Hopefully that will solve the High temp problem.

 

[Bunti]

I assume that 85 C means nothing more than 85 Celsius and this is the temperature the vernatherm opens the way for the oil through the oil cooler. 85 Celsius equals to 185 Fahrenheit. If your vernatherm was not broken before, I do not assume that you see any changes with another one. 

[Prior owner]

5 hours ago, Bunti said:

I assume that 85 C means nothing more than 85 Celsius and this is the temperature the vernatherm opens the way for the oil through the oil cooler. 85 Celsius equals to 185 Fahrenheit. If your vernatherm was not broken before, I do not assume that you see any changes with another one. 

 Yes, it means that it is fully extended at 185F. I have searched online and cannot find Temp specs for different vernatherms. I do know that there are different styles, and that the older ones can lose the tip nut (it ends up flowing away with the oil to somewhere undesired). It appears that my part number Vernatherm was not specified for the Lycoming O-360 A engines. Some of the Lycoming vernatherms are stamped ‘77C or 173F. Aircraft Spruce drop ships these , presumably from Lycoming- I will have to call Spruce to see what is marked on the newest revision vernatherm that I have ordered. 
 

You may very well be correct. If the new one is also marked 85C, I may not see any difference in temps, provided the one I presently have is the same length dimension as the one I ordered.... 
 

This leads me to another question: if the new vernatherm opens at the same temp as the old one, and there are vernatherms that open at a lower temp, wouldn’t installing the lower temp vernatherm bring our oil temps down? At least the system wouldn’t be playing catch up after every climb....

if anyone has the later vernatherm, do you know what he temp marking is? Does anyone know whether the vernatherms are manufactured in varying lengths? 
 

So Yes, my saga may continue beyond the vernatherm...

Edited July 1, 2020 by PilotCoyote

[Prior owner]

Lycoming tech support just confirmed that the part number I removed is the same spec as the part number that is specified for my engine. He pulled the drawing for part number 69451(the one I removed) and it's supposed to extend .16 inches at 180F.

I've got to run a function test on mine now... Is it's okay, then the oil cooler goes out for service.

[redcatcher27]

+1 on cruise climb above 1k’agl... 120 IAS...

In addition to better engine cooling, it also provides a lower deck angle, which gives better surveillance out front, to see and avoid.

Good luck on solving your problems.

[mike20papa]

When was the last time your oil cooler was flushed out.  (probably never) The manual on these oil coolers require periodic flushing as a part of continued airworthiness.  

[Prior owner]

5 minutes ago, mike20papa said:

When was the last time your oil cooler was flushed out.  (probably never) The manual on these oil coolers require periodic flushing as a part of continued airworthiness.  

Prior owner said that oil cooler was flushed at engine overhaul...but there is no record of it, so that will be next on the list. Might just buy a new Aero Classics cooler Instead.

Lycoming also recommends that the vernatherm be replaced at engine overhaul, as the wax expanding plug will only function properly for so many cycles. 
 

I also want to note that my California winter/spring oil temps run about 5-10 degrees cooler when using 20w50. I switched back to 100w at the last oil change as the hot weather was right around the corner....But even if multi viscosity helps move more oil through the cooler, I think it’s still a crutch- 100w should work fine if everything else is working right. Vernatherm testing tonight!
 

[takair]

This may or may not help, but check the fit of the top and bottom of the cooler to the cowl.  You may get a few degrees by sealing it.  Did it many years ago chasing high oil temp and it seemed to help, just can’t recall how much.  I think your D install is similar to my E.

[MikeOH]

I've fought the same high oil temp in climb, especially in summer, for the nearly 3 years I've owned my F.  I've seen as high as 230...YIKES!

I've checked my vernatherm (note that the opening temp really isn't the problem once it is fully open, it is fully open...that is, if the temps continue to rise well above the opening temp the opening temp can't be the problem). I checked to make sure it is fully opening.

I've sent my oil cooler out for overhaul to Pacific Oil Cooler (I wanted to ELIMINATE the cooler as the problem and simple flushing would not do that).

I put in new oil lines..

Honestly, the biggest improvement came with putting in new baffles; my CHTs came down, and so did my oil temps.  However, oil temp is still around 200 in cruise, and may see 215-220 in climb.  I've just learned to live with it.

Good luck!  And do share if you succeed.  I'd love to have something else to try!

[Ross Taylor]

1 minute ago, MikeOH said:

I've fought the same high oil temp in climb, especially in summer, for the nearly 3 years I've owned my F.  I've seen as high as 230...YIKES!

I've checked my vernatherm (note that the opening temp really isn't the problem once it is fully open, it is fully open...that is, if the temps continue to rise well above the opening temp the opening temp can't be the problem). I checked to make sure it is fully opening.

I've sent my oil cooler out for overhaul to Pacific Oil Cooler (I wanted to ELIMINATE the cooler as the problem and simple flushing would not do that).

I put in new oil lines..

Honestly, the biggest improvement came with putting in new baffles; my CHTs came down, and so did my oil temps.  However, oil temp is still around 200 in cruise, and may see 215-220 in climb.  I've just learned to live with it.

Good luck!  And do share if you succeed.  I'd love to have something else to try!

I'm in exactly the same boat.  It almost seems "normal"...

[the_elkhartian]

200 seems to be normal cruise Oil temp in my C (IO-360 with 201 Lasar cowl). 
 

Did a flight review for a friend of mine with a K a couple of weeks ago and I was nervous because HE was nervous when his oil temp went over 200. mine seems to always be over 200....

I don’t know if it should but this thread makes me feel better?

[Prior owner]

Thanks for the tips! 
 

Well, the vernatherm failed the test- Lycoming said That it must extend a MINIMUM of 0.160“ from 150F to 185F.  It was .020 short by 185F.  Doesn’t seem like a big difference, but I guess I’m going to find out when I replace it!

Besides the expanding wax Plug getting tired, the pressure relief spring gets tired as well... so no telling just how unhealthy it is, or what the spring seat pressure is at 185F, or even 200F for that matter. A New one has been ordered. In the meantime I’ll rework The oil cooler / cowling sealing To get minimal air leakage there. Will report back after new vernatherm is installed. I don’t have high expectations, but hope to see some improvement.
 

if you’re getting 200 F oil temp in cruise with These hot summer temps, I think you’re probably doing pretty well- the E and F have the “HE” high efficiency coolers- wish we C and D owners could (legally) upgrade to something better.

 

 

[Ragsf15e]

14 hours ago, MikeOH said:

I've fought the same high oil temp in climb, especially in summer, for the nearly 3 years I've owned my F.  I've seen as high as 230...YIKES!

I've checked my vernatherm (note that the opening temp really isn't the problem once it is fully open, it is fully open...that is, if the temps continue to rise well above the opening temp the opening temp can't be the problem). I checked to make sure it is fully opening.

I've sent my oil cooler out for overhaul to Pacific Oil Cooler (I wanted to ELIMINATE the cooler as the problem and simple flushing would not do that).

I put in new oil lines..

Honestly, the biggest improvement came with putting in new baffles; my CHTs came down, and so did my oil temps.  However, oil temp is still around 200 in cruise, and may see 215-220 in climb.  I've just learned to live with it.

Good luck!  And do share if you succeed.  I'd love to have something else to try!

I think some of these high oil temps might be related to the crazy airflow that happens inside our cowls.  Obviously lower chts help, but if your vernatherm and oil cooler are good, then the other variable is how much air is coming through the oil cooler from the outside to the inside.  Does anyone think it’s possible to get the baffling so good that there’s high pressure inside the cowl that prevents airflow through the cooler?  What about the changed airflow due to that metal plate behind the cooler being installed or not?  
 

If the small metal baffles on the bottom of #2 cylinder aren’t exactly right and there’s no metal plate behind the oil cooler, could high pressure, warm air be going down through #2 fins and hitting the back of the oil cooler?

 I Probably have lower OATs than you guys up in Washington, but I get 190ish in climb and 180-185 cruise.  Lasar cowl closure, but stock oil cooler.

[Shadrach]

No one has mentioned the shield that should be positioned over the oil lines that run to the oil cooler. Many older Mooneys came from the factory sans fire sleeve on engine hoses. I think it’s prudent to ensure that all hoses are sleeved and are positioned properly within the cowling.   The to and from oil cooler hoses run right under the exhaust stacks for cylinders #2 and #4. If not positioned correctly under the shield, higher oil temps are likely.

Edited July 2, 2020 by Shadrach

[Ragsf15e]

On 7/1/2020 at 7:53 PM, MikeOH said:

I've fought the same high oil temp in climb, especially in summer, for the nearly 3 years I've owned my F.  I've seen as high as 230...YIKES!

I've checked my vernatherm (note that the opening temp really isn't the problem once it is fully open, it is fully open...that is, if the temps continue to rise well above the opening temp the opening temp can't be the problem). I checked to make sure it is fully opening.

I've sent my oil cooler out for overhaul to Pacific Oil Cooler (I wanted to ELIMINATE the cooler as the problem and simple flushing would not do that).

I put in new oil lines..

Honestly, the biggest improvement came with putting in new baffles; my CHTs came down, and so did my oil temps.  However, oil temp is still around 200 in cruise, and may see 215-220 in climb.  I've just learned to live with it.

Good luck!  And do share if you succeed.  I'd love to have something else to try!

After telling you guys how great my oil temp is, I just flew 3.5 hours from Spokane , WA to Ogden, UT.  Southwest flow aloft means headwinds and high temps.  9C at 11,500’.  12C at 9,500’.  Both my oil temps and cylinder temps were hotter than normal.  I have been cruising at 7,500 and up all winter with negative temps.  I had to work to keep the oil below 200.  Seemed like OAT was biggest factor, but keeping my clinders below 360ish helped too.  I normally run 100 ROP that high but had to cool it a bit more.  
 

Also, I departed with 6 qts in.  Probably 5.25 now.  I’m gonna fill to 6.5 for the return.

You guys are right, it wasn’t fun watching the oil temp slowly climb in level cruise.

[Ross Taylor]

On 7/2/2020 at 9:23 AM, Shadrach said:

No one has mentioned the shield that should be positioned over the oil lines that run to the oil cooler. Many older Mooneys came from the factory sans fire sleeve on engine hoses. I think it’s prudent to ensure that all hoses are sleeved and are positioned properly within the cowling.   The to and from oil cooler hoses run right under the exhaust stacks for cylinders #2 and #4. If not positioned correctly under the shield, higher oil temps are likely.

Good call on this.  But in our case, we have fire sleeve shielded lines and the curved metal shield. I just confirmed that today.  I did, however, see that my oil cooler is engraved (like with one of those vibrating etching pens) with a date from 1965.  I don't know when it was last overhauled, so that may be up next on my list.  Pacific Oil Coolers, here I come...

[Shadrach]

1 hour ago, Ragsf15e said:

After telling you guys how great my oil temp is, I just flew 3.5 hours from Spokane , WA to Ogden, UT.  Southwest flow aloft means headwinds and high temps.  9C at 11,500’.  12C at 9,500’.  Both my oil temps and cylinder temps were hotter than normal.  I have been cruising at 7,500 and up all winter with negative temps.  I had to work to keep the oil below 200.  Seemed like OAT was biggest factor, but keeping my clinders below 360ish helped too.  I normally run 100 ROP that high but had to cool it a bit more.  
 

Also, I departed with 6 qts in.  Probably 5.25 now.  I’m gonna fill to 6.5 for the return.

You guys are right, it wasn’t fun watching the oil temp slowly climb in level cruise.

200-210 is fine. No need to work to keep it below.

[Ragsf15e]

27 minutes ago, Shadrach said:

200-210 is fine. No need to work to keep it below.

I do agree, it was just different than i was use to.  I gotta fly in warmer weather more often and get use to how it runs.  

[MikeOH]

1 hour ago, Shadrach said:

200-210 is fine. No need to work to keep it below.

I'm a fan of well taken data.  And, I happen to think Savvy does a decent job.  Consequently, I have some concern based on my plane's oil temp versus my cohort: I'm higher than 95%.

[Shadrach]

13 hours ago, MikeOH said:

I'm a fan of well taken data.  And, I happen to think Savvy does a decent job.  Consequently, I have some concern based on my plane's oil temp versus my cohort: I'm higher than 95%.

Being a fan of data you know that without OAT, that data does not tell you a lot. Using month as a proxy for OAT is not optimal.

Seeing the data for your plane and the conditions under which the data was generated would be more useful.

I know that LA heat is a “dry heat” but your oil doesn’t care...

[FloridaMan]

I climb at full power. Check your vernatherm. 

[MikeOH]

6 hours ago, Shadrach said:

Being a fan of data you know that without OAT, that data does not tell you a lot. Using month as a proxy for OAT is not optimal.

Seeing the data for your plane and the conditions under which the data was generated would be more useful.

I know that LA heat is a “dry heat” but your oil doesn’t care...

 

1) I provided one year's worth of data; you can see the variation by season.  At only ONE point are my temps close to the median.

2) You are ignoring that the cohort of data is from the entire country; all kinds of OATs, yet my temps are higher than 95%.  ALL of that data ends up with a median level of 187; awfully close to the vernatherm regulation set-point.  I don't think that's a coincidence; you're free to think it is.

That data indicate to me that aircraft with properly functioning oil systems regulate at 185-190 REGARDLESS of OAT.  Those of us with less than perfect systems end up with high temps when the OATs rise above some relatively mild level.  For non-mountain southern California that's low-50s for coldest daytime temps.

Hell, the POH says anything below 225 is "in the green," with 245 max.  Is that you definition of "fine?" If so, are you "fine" flying all day with oil temp at 225, when the cohort for NA Mooneys shows the median temp to be 187?

Those of us with temps over 200 are concerned, and would like to do something to lower them even if they are "in the green." Since we are NOT exceeding red line we are living with it.  But I, for one, am NOT happy about high oil temps if statistically 'normal' is 187.

[Prior owner]

Maybe the top of the green range exists for summertime flying? I very much doubt the heat exchange system in the older models that have cowl-mounted coolers are efficient enough to provide the same oil temperature at 50F OAT as when cruising at 90F OAT.... Perhaps the factory expected temps to run that high when the weather gets hot...?

[MikeOH]

29 minutes ago, PilotCoyote said:

Maybe the top of the green range exists for summertime flying? I very much doubt the heat exchange system in the older models that have cowl-mounted coolers are efficient enough to provide the same oil temperature at 50F OAT as when cruising at 90F OAT.... Perhaps the factory expected temps to run that high when the weather gets hot...?

Perhaps.  But, that still ignores the reality of the Savvy data I posted.  The median temp is 187.  I find it hard to believe that there are as many planes being flown in cold temps that exactly balance out those flown in hot temps.  Further, if the vernatherm is functioning correctly then even those in cold temps should see the oil temp rise to 187 (or thereabouts), hence the median should be even higher if there are other planes flying in higher OATs for which the factory heat exchange system is, by design, insufficient.

Yet, the median IS 187.  That implies planes like mine with higher oil temps are, in fact, outliers with some kind of issue.

I'd really like to see a cogent argument otherwise; believe me, I'd like to think my temps are 'just fine.'

[carusoam]

We have a viscosity control system...

Not so much an oil temp control system...

Sure, the oil is used as a coolant...

and when it gets too hot, The oil gets too thin...

In this case, to maintain the oil’s viscosity people choose a summer viscosity for their oil...

 

Looking at the oil T... if it is hot... and the vernatherm is open...

The only thing controlling the amount of cooling... is the surface area of the oil cooler(Size), the air flowing through it, and the cleanliness of the tubes... both inside and outside.
 

Things we can do...

1) Verify the valve opens fully at the designed temperature...

2) verify we have the right vernatherm as expected...

3) See what type of maintenance has been done on the oil cooler... cleaning or OH...

4) In the winter, we block some of the surface area...

So... anywhere in the green zone, is expected to supply the proper oil viscosity...

In order to control oil temp with a tighter control limit... expect to use a digital controller with a motorized valve...

Where we run out of viscosity control... is when we reach oil temps above the degradation temp of our oil...

That red line is there to protect the oil from degradation...

PP thoughts only, not a mechanic, chemist or lubrication guy...

Best regards,

-a-