Oil cooler in winter ops

[MooneyPTG]

I have a 74e and was wondering if the oil cooler works lIke a radiator with a valve that opens up to the cooler when it reaches a specific temperature. Or is oil always going to the cooler. My cooler looks like a small radiator. I have flown below 0 degrees and have never had any problems with oil temp but saw some discussions on this topic.

Thanks

[Mooneymite]

Good overall discussion about oil temps at:

http://www.avweb.com/news/maint/182617-1.html?redirected=1

Excerpt of interest:

Oil can also bypass the oil cooler if the vernatherm valve is defective. The vernatherm is just like the thermostat on your car's radiator. It's a temperature-sensitive valve that regulates oil temperature by controlling oil flow through the cooler. As a rule, it strives to keep oil temp at around 170 degrees F.

You can check the vernatherm's basic operation the same way you would a car's thermostat. Just drop it in boiling water and it should open wide. That's nice, but it really doesn't tell you what you need to know.

Be scientific and methodical about this: Get a good, accurate thermometer (or temperature probe on a multimeter) and put it and the vernatherm in a pan of cold water. Start heating the water. (Some mechanics insist that water is not as accurate as oil, and use oil instead, but it's a messier proposition.)

Continental vernatherms, for example, should open when the water temperature gets up to 180 or 190 degrees. If it doesn't, chuck it and get a new one. A Continental vernatherm marked 77 C should travel at least 0.090 inches as the water temperature climbs from 120 degrees up to 170 degrees. Those marked 173 degrees should travel at least 0.16 inch as water temperature rises from 135 to 173 degrees.

Lycoming Vernatherms....

[rainman]

There are some good discussions on oil cooler blocking devises for winter ops. See if the search function gets you the info you need.

[N601RX]

On A Lycoming the Vernatherm is in a parallel path with the oil cooler.  It actually closes off to force oil through the cooler.  When its open the oil does not flow through the cooler, it bypasses the cooler.

[pinerunner]

On A Lycoming the Vernatherm is in a parallel path with the oil cooler.  It actually closes off to force oil through the cooler.  When its open the oil does not flow through the cooler, it bypasses the cooler.

and this leads to the scary scenario where the oil in the cooler gets REALLY cold on a winter day and very viscous. Then the rest of oil heats up to where the vernatherm closes, forcing the oil through the obstructed oil cooler and literally popping it or at least deforming it until the oil flows and the pressure is relieved. Winter, arctic, flyers have to do things to keep the oil cooler from overcooling.  

[M20F]

and this leads to the scary scenario where the oil in the cooler gets REALLY cold on a winter day and very viscous. Then the rest of oil heats up to where the vernatherm closes, forcing the oil through the obstructed oil cooler and literally popping it or at least deforming it until the oil flows and the pressure is relieved. Winter, arctic, flyers have to do things to keep the oil cooler from overcooling.

If you get a Reiff pre-heater for a couple extra bucks they give you a pad to heat the oil cooler as well. I have never had any issues in keeping oil temp up once pre-heated. Anyone looking to fly when it is cold should really invest in a Reiff or Tannis system as it isn't just the oil that needs to warm but all the differing metals in the engine as well. Quick, easy, and well worth basically 1 AMU to purchase and install.

[Andy95W]

I have a 74e and was wondering if the oil cooler works lIke a radiator with a valve that opens up to the cooler when it reaches a specific temperature. Or is oil always going to the cooler. My cooler looks like a small radiator. I have flown below 0 degrees and have never had any problems with oil temp but saw some discussions on this topic.

Thanks

Living in Michigan, I've been wondering about it, too.

I looked at an earlier thread and found where a few people were commenting on how modern multi-grade oils like 15w-50 or 20w-50 will become very viscous below about -35°C. I could see that as a problem with the scenarios described above. So my personal limit for OAT is -25°C.

Below -25°C (-13°F) at altitude I will put put some aluminum foil tape on the oil cooler and remove about 1/3 of the area from the center before I go fly. (I figure a standard 2° C/1000' lapse rate).

Below -25°C on the ground I will make sure my oil cooler gets pre-heated along with the engine.

Then again, who am I kidding? I'm not going flying when it's that cold.

[Mooneymite]

 Winter, arctic, flyers have to do things to keep the oil cooler from overcooling.  

 

Yeah, like move to Florida!  

[pinerunner]

Yeah, like move to Florida!  

Watch out for the pythons. Oh I just got promoted to "Lives Here"; is that a good thing?