Air / Oil Separator -> Engine Corrosion

[Matt]

Five years ago, shortly after the restoration of Sedan N1331H had been completed, I installed a simple air/oil separator to avoid the oily mess on the fuselage belly. It worked wonderfully and all that remained to be wiped off, from time to time, has been lead residue from the exhaust gases.

Within the past five years, I ran into cylinder corrosion issues, twice, which we attributed to the low oil temperature (160-176 °F; never above 180!) during the cold season. Also, I have been using a Reiff engine preheater (band heaters around cylinder and heat elements on oil sump), during winters. But I only activated the system, a couple of hours before a flight (via text message) and not once activated it without going flying afterwards.

I always made sure, a flight would last at least 40 minutes to one hour, during the cold season, in order for the oil to reach its maximum temperature. The Sedan's engine cowl obviously provides excellent cooling, confirmed by oil temperatures of maximum 206 °F without oil cooler on the hottest of summer days here in central Europe (OAT around 97 °F). I experimented with blocking off part of the cooling openings, during the winter. This helped to raise the oil temperature slightly, but not enough.

A discussion with Dave Swartz in Alaska (aviation engineer and Sedan owner himself), this past summer, convinced me that it would be wise to remove the air/oil separator in order to avoid any condensation humidity running from the breather tube through the separator and back into the engine. During the recent annual inspection, we did remove it and also are working on different measures to raise the oil temperature (slowing down the air stream by reducing the opening section where the air exits the cowl).

The attached picture dramatically shows the water content (bright droplets) in the oil that had accumulated inside the rocker cover of the number 5 cylinder (far rear/right side), into which the air/oil separator's hose returns the oil. Dave's explanation that a clear separation of the oil from the water cannot be achieved in the environment of a shaking and vibrating engine makes perfect sense. There will always be a "transition layer" with mixed water and oil, hence there will also be some water returned into the cylinder and engine through the separator hose.

I am aware that this issue would not be as critical, if the engine oil reached 180 °F or higher. But I thought this post might be interesting for any other Sedan owner operating in a colder climate.

Matt

[dikholder]

Matt:

I talked to Burl last year about a winterization kit for the C-145 Sedan. He said he was working on one. I dont know if he has it ready to sell or not.

Dik Holder N1441H Queen of the Berry Patch

[Matt]

Yes, Dik,

that is correct, thank you for the hint. I was in contact with Burl about such a kit, too. But his priority is now on getting the factory new AeroSedan ready for the market. I suspect, it will be a moment, before the winterization kit becomes available. I hope – and it looks promising – to have the temperature problem solved for N1331H, this winter. By the way, what temperature does the Queen's engine oil reach in the Alaskan winter? (With or without oil cooler?)

Thanks again and a happy new year with many safe and fun flights!

Matt

[jepropst]

Matt,
I have a air/oil separator on my Champ with a C-85. Instead of routing the sludge/water line back to the engine, I routed it to an externally mounted clear plastic bottle to collect the sludge and water. I tend to get more water in the winter versus summer. My oil and cylinder temp does run higher than yours. I empty the sludge bottle a couple times a year. On average i would guess that i collect about a cup of sludge each year. I had to get a field approval to add this bottle as it was a deviation from the manufacturer's STC installation instructions.

[Matt]

Hi John and apologies for the late reply.

Sounds like an interesting solution. Would you mind posting or emailing a photo of the installation?

Thanks, Matt

[jepropst]

here's a link to the field approval that I obtained for installing the collection bottle on my air/oil separator:http://johnpropst.yolasite.com/resource ... 20wolf.pdf
I tried adding a photo of the bottle but apparently the photo que is full. It is just a semi-transparent plastic bottle mounted on the fire wall with the water/sludge line from the separator entering the top of the bottle.

[Matt]

Great, thank you very much, John!

[joea]

Matt,

I have a separator on the Sedan as well and have temp issues like you do. I finally blanked the air inlet to the oil cooler totally off and that helped but still would like to see my oil temps a bit higher, say 210 or so...

Hmm, John P's idea might be worth a try...

Joe A

[Matt]

Thanks Joe!