Vernatherm and Low Temperature

[RVadmirer]

With the recent "cold" weather in northern California I can't seem to get my oil up to over 140 degrees. And then it cools to 120 in descent. Everything I've read indicates the vernatherm is a potential culprit for overheating but it seems it could also be stuck open and not letting the oil warm up enough.

My dilemma is that it is brand new and on the back of a new 90 degree oil filter, all of which has to be removed to test it, and this is really difficult to do - much like the vac pump... But this looks like my only option? The thread about shutters seems to apply to aircraft that don't have a vernatherm? If it is working properly there would be no flow to the cooler and no need for a shutter - right?

Any advice and suggestions are always greatfully appreciated!

[dan]

Check your calibration. Could be that it's off...much simpler than anything mechanical. Dip your oil temp probe in 212F (boiling water) and see what your gauge reads...

[mark manda]

Are you reading the thread on the yahoo RVsocallist about the shutters and the guy flying his new 7a? similar problems.

[mahlon_r]

The Vernatherm system has a preprogrammed leak in it. The system always allows a small amount of oil flow through the cooler even when the vernatherm is open. This is done to prevent oil form being able to congeal in the cooler when the vernatherm is saying no oil should be flowing through it and the cooler is subjected to very cold air. So...... if the outside temps get cold enough this little bit of flow that is there to prevent congealing is enough to actually provide some cooling and thus the oil temps could be cooler then what you want or expect. The only fix for this situation is to limit the airflow over the cooler with some sort of winter baffle plate. Of course the vernatherm could be stuck open but if the OAT is cold what you are describing will happen normally.
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 your own risk."

[IowaRV9Dreamer]

My Skipper has cold oil temps. In the summer, I am lucky to see 170 degrees on a 95 degree day.

Recently the OAT was 32 degrees and I could only get to 148 degrees.

I taped off the airflow to the oil cooler, and the oil temps got to 172!

Do these results indicate that my vernatherm is stuck open?

Thanks for any help!

[mahlon_r]

If anything it would be stuck closed not open. With that being said. I think that you engine just doesn't generate enough heat with the cooling available from your nacelle. Many O-235 installations on other aircraft don't have an oil cooler because the oil temp can be maintained without it. Does the aircraft have an oil cooler winterization plate you could install and use more permanently?
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 your own risk."

[David-aviator]

Originally Posted by dan

Check your calibration. Could be that it's off...much simpler than anything mechanical. Dip your oil temp probe in 212F (boiling water) and see what your gauge reads...

...been there twice and it is right on.

With the SW 8432R completely blocked off, oil temp struggles to get up 150 on a 20F day. It takes 15 minutes to get it up to 100F before take off.

The "vernatherm" (Does anyone know where that term came from? It is not in the Lycoming lexicon of words) is a hot weather device that assures oil will flow to the cooler. In cold weather it may as well not be installed, it has no useful function as it does not block oil flow to the cooler.

I am of the opinion if one has good cooling in the summer months, it is way too good in cold weather. The only way to change that is to cut down air flow through the engine compartment.

That issue could be resolved with cowl flaps or a baffle to restrict exit air. Messing with inlet air flow could really disturb individual cylinder head temps and probably is not the way to go.

I keep thinking global warming will return but there is snow in the forecast for today and also Christmas Eve. If it becomes one of those typical freezing rain, turning to snow events so common around here, the issue may be mute. Our field will be closed for weeks. I am beginning to not like a grass runway.

[revenson]

Vernatherm is part of the name of the company that makes 'em.

[IowaRV9Dreamer]

Originally Posted by mahlon_r

I think that you engine just doesn't generate enough heat with the cooling available from your nacelle. Many O-235 installations on other aircraft don't have an oil cooler because the oil temp can be maintained without it. Does the aircraft have an oil cooler winterization plate you could install and use more permanently?

Hi Mahlon - nope, no winterization plate for this airframe. What makes me wonder about the vernatherm is that even on a hot summer day my oil temps barely make it to 170. Make me think I need a "summerization" plate too. Its hard to believe that the oil cooler is that much oversized, but maybe it is?

I'm measuring oil temp with an EI bar graph analyzer. The probe is on the galley plug at the front of the engine. The certified probe is at the rear of the engine, and both instruments agree.