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Bravo Oil Temps

alextstone

By alextstone
in Mooney Bravo Owners

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alextstone Mentor

alextstone

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Question for Bravo owners:  What is the range of oil temps you see in your Bravo?  Mine ranges from 195 degrees to 215 degrees, depending on OAT and altitude.  I wonder if it would be advantageous to have the oil cooler overhauled or if this is "normal".  

Rick Junkin Mentor

Rick Junkin

Posted
Posted

Hi Alex,

I see a max of 195 at the peak of the climb to the upper teens and then about 186 plus or minus 3 degrees in cruise LOP, 2200/30 and 13.8ish GPH. Even varying off that power setting I never see anything above 195 on the oil temp.

Cheers,
Rick

  • Like 1
carusoam Grand Master

carusoam

Posted
Posted

Before OH...  it is always normal to...

  • check the operation of the vernatherm... mechanical oil temp control valve... (heat in water with a thermometer to see what temperature it activates at...)
  • wash the fins of the oil cooler...  dirt and FOD can block airflow...
  • Flush the oil cooler out...  sludge can block oil flow...
  • An IR thermometer is often used to detect sludge blocked tubes in the oil cooler...

Having the same peak temperature is a hint that both oil coolers are operating the same, and not running out off cooling capacity...

If the cooling capacity is artificially cut back... than oil temps rise higher than the vernatherm can control...

When the vernatherm is fully open, the oilT is dependent on as much cooling the radiator can get... limited by OAT, Airflow, tubes operating, and clean surface area...

PP thoughts only, not a mechanic...

Best regards,

-a-

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LANCECASPER Grand Master

LANCECASPER

Posted
Posted
On 4/10/2020 at 4:56 PM, alextstone said:

Question for Bravo owners:  What is the range of oil temps you see in your Bravo?  Mine ranges from 195 degrees to 215 degrees, depending on OAT and altitude.  I wonder if it would be advantageous to have the oil cooler overhauled or if this is "normal".  

As Anthony @carusoam   points out, I would be equally suspicious of the vernatherm as the oil cooler, maybe more so.

How is your oil pressure? It would seem if your oil cooler is restricting flow that the pressure would be on the high end.

alextstone Mentor

alextstone

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2 hours ago, LANCECASPER said:

As Anthony @carusoam   points out, I would be equally suspicious of the vernatherm as the oil cooler, maybe more so.

How is your oil pressure? It would seem if your oil cooler is restricting flow that the pressure would be on the high end.

How might one test the vernatherm?  Oil pressure is normal...higher when cold, lower when hot  of course but in the green always.

LANCECASPER Grand Master

LANCECASPER

Posted
Posted
18 minutes ago, alextstone said:

How might one test the vernatherm?  Oil pressure is normal...higher when cold, lower when hot  of course but in the green always.

@carusoam Anthony describes how in his post above.

However you're in the green with your temperatures. Temps too low aren't good for moisture either.

At your high end, 215, your oil definitely isn't boiling, but it is boiling off any moisture. Ten or fifteen degrees cooler would be better since your probe is on the top of the engine and is probably at a cooler point than some other points, but it's within range. Oil changes on Bravos are every 25 hours anyway, but the oil takes a beating since it is cooling the turbo. 

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alextstone Mentor

alextstone

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6 minutes ago, LANCECASPER said:

@carusoam Anthony describes how in his post above.

However you're in the green with your temperatures. Temps too low aren't good for moisture either.

Wow, it would help if I read the post before asking for help!  

  • 2 weeks later...
alextstone Mentor

alextstone

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Posted
On 4/10/2020 at 6:08 PM, carusoam said:

Before OH...  it is always normal to...

  • check the operation of the vernatherm... mechanical oil temp control valve... (heat in water with a thermometer to see what temperature it activates at...)

Hey, @carusoam Anthony, thank you!  I pulled and tested the vernatherm...it did not activate until about 210 degrees...time for a replacement.

vernatherm-212.thumb.jpg.7815cececc69246d5935db675af270a0.jpg

 

vernatherm-open.thumb.jpg.b7763592d8beefacb000f01d2bbcbd5f.jpg

 

Help me to understand something though...the vernatherm spring did not expand until the temp decreased back to 170 degrees, so in use, would the engine oil temp rise to 210, the valve then force all oil to the cooler thus causing it to cool some?  Should I expect to see this peak then slight decline in oil temp in use?  I am not.  I must not fully understand the function of the valve....

As always, thanks for the advice.

Alex

vernatherm-170.jpg

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carusoam Grand Master

carusoam

Posted
Posted

The power of MS is  amazing... isn’t it?

Of course, the power of my knowledge is pretty limited... not so amazing... :)

 

The design of the vernatherm is pretty much a temperature controller...

In order to control the temperature of the oil it has to adjust to allow more or less oil to flow through the cooler...
 

The hotter it gets the more open it is...

It may reach a certain point where it won’t open anymore, or it opens more, but no more oil can flow into the cooler...

This will be a system limitation...

 

In real life, this system has become precision designed and updated... and time/age limited...


I found a vernatherm catalog that shows the construction of the device... and a bit of how they work...

https://www.vernatherm.com/docs/vernatherm_web_catalog.pdf

Somewhere around page four describes thermal actuators... :)

Page five shows the hysteresis curve that you described... expanding with one temperature curve and contracting in a slightly different temp curve...

For better details, one many of MS’s mechanics may know these things better than me...

We can always ask Doc...

Best regards,

-a-

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carusoam Grand Master

carusoam

Posted
Posted

@alextstone, more details about the closing being different than the opening...

Page five shows the hysteresis curve that you described... expanding with one temperature curve and contracting in a slightly different temp curve...

The hysteresis curve is selected so the valve isn’t opening and closing a lot at the temperature set point...

Amazing control that requires no electronic controller or power to operate it...

Best regards,

-a-

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alextstone Mentor

alextstone

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Great info,@carusoam ! In page 8, there's a graphic of the SAME Lycoming vernatherm. Looks like you stumbled on the actual manufacturer.

I'll order a new onece installed, I'll give a PIREP in the delta in temps.

Alex

Sent from my Pixel 3 XL using Tapatalk

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LANCECASPER Grand Master

LANCECASPER

Posted
Posted
10 hours ago, alextstone said:

Great info,@carusoam ! In page 8, there's a graphic of the SAME Lycoming vernatherm. Looks like you stumbled on the actual manufacturer.

I'll order a new onece installed, I'll give a PIREP in the delta in temps.

Alex

Sent from my Pixel 3 XL using Tapatalk
 

If you get a part number on that vernatherm please post it, Bravo owners who need one in the future will appreciate that.

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alextstone Mentor

alextstone

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46 minutes ago, LANCECASPER said:

If you get a part number on that vernatherm please post it, Bravo owners who need one in the future will appreciate that.

Sure thing.  Here is the relevant Service Letter as of 04.26.2020:  https://www.lycoming.com/sites/default/files/SI1565A Thermostatic Oil Cooler Bypass Valve.pdf

It stipulates that ALL lycoming engines that have a vernatherm with only a couple of obscure exceptions (Navajo and Duke aircraft), use the following part number:  53E22144

Here is the link at Aircraft Spruce:  https://www.aircraftspruce.com/catalog/eppages/lycomingseatvalve_08-12154.php?clickkey=33907

The vernatherm ships with the required aluminum gasket, BTW.

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LANCECASPER Grand Master

LANCECASPER

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Posted
2 minutes ago, alextstone said:

Sure thing.  Here is the relevant Service Letter as of 04.26.2020:  https://www.lycoming.com/sites/default/files/SI1565A Thermostatic Oil Cooler Bypass Valve.pdf

It stipulates that ALL lycoming engines that have a vernatherm with only a couple of obscure exceptions (Navajo and Duke aircraft), use the following part number:  53E22144

Here is the link at Aircraft Spruce:  https://www.aircraftspruce.com/catalog/eppages/lycomingseatvalve_08-12154.php?clickkey=33907

The vernatherm ships with the required aluminum gasket, BTW.

That's great - seems like a relatively inexpensive fix ($340). Let us know your results.

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alextstone Mentor

alextstone

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19 minutes ago, irishpilot said:

Let us know how the new part works. My Bravo sees between 195-205 from an avg of 11k-23k alt.

Sent from my Pixel 3a using Tapatalk
 

Hmm, interesting.  You might benefit from testing yours too.

 

alextstone Mentor

alextstone

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On 4/26/2020 at 1:56 PM, irishpilot said:

Let us know how the new part works. My Bravo sees between 195-205 from an avg of 11k-23k alt.

Sent from my Pixel 3a using Tapatalk
 

Updated PIREP:  The temps are down by about 15-20 degrees with the new vernatherm installed...Here's a photo of the new one on the left and the old one on the right in oil at 180 degrees F.  You can see the one on the left functioning at this temp and the one on the right is not...

vernatherms.thumb.jpg.19ad6075d8172216b5d24a3a58c2fb39.jpg

 

Here's the EDM during adjustment for LOP operations (yes, my Bravo flies smoothly LOP after some work getting it there)  Notice the oil temp at 190 degrees F.  The hottest I have observed is 194 degrees in climb (previously 210-215 degrees):

temps.thumb.jpg.220933e6523a40f1d601f4ec94a395ad.jpg

BTW, Cylinder #5 was replaced about 3-4 flight hours ago so it's CHT is still a little on the warm side.  

Now, on to the next problem...a fuel leak in the the pilot's wing.  Never ends.

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irishpilot Proficient

irishpilot

Posted
Posted



Updated PIREP:  The temps are down by about 15-20 degrees with the new vernatherm installed...Here's a photo of the new one on the left and the old one on the right in oil at 180 degrees F.  You can see the one on the left functioning at this temp and the one on the right is not...




Thanks for the update! I will follow suit on my upcoming Mx and see if it helps.

Sent from my Pixel 3a using Tapatalk

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LANCECASPER Grand Master

LANCECASPER

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14 hours ago, alextstone said:

Updated PIREP:  The temps are down by about 15-20 degrees with the new vernatherm installed...Here's a photo of the new one on the left and the old one on the right in oil at 180 degrees F.  You can see the one on the left functioning at this temp and the one on the right is not...

 

 

Here's the EDM during adjustment for LOP operations (yes, my Bravo flies smoothly LOP after some work getting it there)  Notice the oil temp at 190 degrees F.  The hottest I have observed is 194 degrees in climb (previously 210-215 degrees):

 

BTW, Cylinder #5 was replaced about 3-4 flight hours ago so it's CHT is still a little on the warm side.  

Now, on to the next problem...a fuel leak in the the pilot's wing.  Never ends.

Let us know if it has lowered your CHTs a little as well. It makes sense that it would if the oil cooling the engine is cooler.

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