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high oil temps and vernatherm testing

steveciha

Active Member
I have read on this list that it is possible to test vernatherm's by emersing them in hot water and watching for them to "open up". Well, i took mine out of the engine, took the retaining clip from the holder assembly and checked it before and after heating it up to 210 degrees. I could not see or measure any detectable change in length. Must this test be performed with the vernatherm spring assembly attached to the holder? Also, how much movement should I expect to see?

steve ciha
 
Another idea

I was wondering if squeezing, or feeling the temperature of the hoses on both sides of the oil cooler after warming up your engine would answer your question. It seems that if the vernatherm is opening the hoses would be hot on both sides as the oil circulates. If the vernatherm is not opening the hose on one side should be a lot cooler. Or vice versa??? Just a thought.

Let us know what you find.
 
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If the vernatherm is totally out to lunch, the cooler will be cold but if the vernatherm isn't seating well, but still kinda functioning as far as expanding goes, the cooler will feel warm or hot. If the cooler is cold the vernatherm normally needs replacement as long as the plumbing is correct.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."
 
I know that at least part of the oil is getting to the cooler, as it is too hot to touch, and a thermometer laying on top of it reads 175 degrees. i fly an 0-360 a1a lycoming and see temps at 215 on 90 degree days. Otherwise, things are OK. I am thinking i need to absolutely verify that the sensor is correct, and maybe buy a long stem thermometer to see what the temp of the oil really is.

steve ciha
 
Brian, thanks for the link to Dan's page concerning the vernatherm. You were right, it is good information. Perhaps my test method was flawed. I removed the vernatherm from the "holder" and that may have altered the way that it would behave. I will remove and re-test as shown.

steve ciha
 
This is another old thread that would have answered my question but the link with the info is no longer available. Does anyone know where I can find how to test a vernatherm. Need opening temp and change in length.
Thanks!
 
I tested a few vernatherms. You do not remove the retaining ring, except to clean them, but not for a test. Place in boiling water and you should see it expand. Once expanded, you measure the length and compare to the cold length. There is a spec you'll need to look up, but I vaguely remember it being a minimum of .180" of expansion.

I had one that needed cleaning in order to operate properly.

Larry
 
Per the manufacturer's spec sheet, it should lengthen by 0.160" minimum as it passes through the temperature range between 150F and 185F. Note you don't just boil it and watch it expand. You need a thermometer, and measure at specified temperatures.

When installed, it should be fully pressed against the seat between 183F and 187F.

The pressure relief cracking pressure is 60-90 psi with oil at 195F.
 
Some vernatherm data

Dan, thanks for all the great information, as always!

I've noted markedly increased oil temps, all else equal, this year vs the previous 19 years. I checked the obvious things, such as debris on the air inlet side of the cooler, erroneous temperature reading (idle oil pressure is lower than typical when the oil indicated 200-210, for example, on taxi in). Here are some test data on the vernatherm:

ACtC-3d3pIjaT-ZvJHDwO2hDVE4xwdHh1UEB2elKj4bacalmaRzVgixP8pBKPDAjDfPQ2WWvBf_43hhGRlCUL5oDAN8hcayjl17azsv3VSjW3472PlImLEZcNlMcuALMxibf0p_Ipa-lUj5_88KHdAm9DYQpdg=w1000


It appears my high oil temperatures are not caused by the vernatherm. I will remove the cooler and have it flushed next. The cooler was flushed about 500 hours ago. Engine has same number of hours since OH.

All ideas welcomed.
 
check the guage and probe for accuracy!
Good Luck,
Mahlon

Yes, thanks, I did verify the probe vs a Fluke probe. Put both in water and slowly brought to a boil. They correlated within a degree or two.

There is another change that happened since last summer - I switched from Exxon Elite oil to Philips Cross Country 20-50. I'd run EE since around 2003 or so.

The little bit of research I did showed that the heat capacity of mineral should be slightly higher than synthetic, but only slightly. What I could not find is how the shear generated heat, at operating temperatures, might compare. Oil gets heated not insignificantly between entering a journal bearing and leaving it. I could perhaps find the viscosities vs temperature of the two, and calculate it for varying assumed bearing clearances. I might have to consult my machine design book, as I haven't done one of those calculations since about 1980...

I've made several additional flights since flushing the cooler, but no real change. Last week I was cruising at 6500', OAT 72F (surface temps 88 @ 1400msl), temp peaked at about 208 during the 120-130 kias climb, and stabilized at 195 or so 5 minutes after leveling off. All are acceptable temperatures. It was the change from the previous 18 years that got my attention.
 
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