Keeping oil temperature up

jmaynard

jmaynard

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Jay Maynard
My O-200 doesn't have an oil cooler. I haven't been able to get the oil temperature above 140 F since it got cold around here a few months ago, and I'm getting nervous about not boiling the condensation out of the oil.

When I first got the airplane, I spoke to a guy who owns a Zodiac north of me, and he recommended I make up a plate to cover the air outlet from the cowling to cut down on the cooling airflow. While I was talking to folks on the Zenith-601 list, one person suggested that I use an oil sump blanket instead, since my CHTs and EGTs are in the normal range. Do those things work? It seems like a simple solution. I've got a Tanis heater on my engine, including a sump warmer; would the blanket be an issue with that?
 
I'm only a mechanically inclined pilot but a few things off the top:

--Why would you want to increase oil temp? After all, heat is the sworn enemy...other parts of the engine are operating hotter than what they oil temp gauge would indicate.

--Do you know where in the system your oil temp gauge is located?

--It seems to me once oil temp is in the normal temps you would be fine.
 
Richard said:
I'm only a mechanically inclined pilot
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Me, too.
-Why would you want to increase oil temp? After all, heat is the sworn enemy...other parts of the engine are operating hotter than what they oil temp gauge would indicate.
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Whereas that is true, the engine is designed to operate at certain temperatures and the engine will go to TBO and beyond at those temperatures.

The question here is water in the oil. Some water dissolved in the oil is unavoidable, as water is a byproduct of combustion, and blowby gasses yada yada. The lubricating qualities of water are... less than that of oil. The water (mixed with some other combustion products) makes acid. Corrosive!

This water will accumulate in the oil unless the oil gets hot enough to "boil" it out. On cold winter morning pre-flights, I've seen ice crystals on the dipstick! That plane had been running too cool.

The working assumption I have been told is that an oil temp of 180 at the gauge sensor will occur when the internal oil temperatures deep in the engine are sufficient to purge the oil of most of the water.

-Skip
 
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Have you called Zenith to see if they have a winterization kit? They may restrict cowling inlets or outflow to reduce the cooling airflow a bit.
 
No, they don't. That was my first call. They referred me to the guy in Crookston, and said that I should let them know what I come up with so they can produce it.
 
Harry Fenton on the flybaby website has some stuff on there about keeping engines warm in the winter, i think. Im also pretty sure he has posted some info from Continental on cold weather ops on the flybaby yahoo group. www.bowersflybaby.com
 
I've been doing some research on this issue. Word is that OUTflow restriction is better than inflow restriction. Makes your heater work better and is less likely to screw up critical airflow over the cylinders. Oil sump and intake tube blankets may help but some report little difference. Wag Aero has them. I would talk to your engine manufacturer about your installation. They may have recomendations.

The Tannis heater you have may already be doing a lot to minimize moisture build up in your engine. It may not get hot enough to boil off water but it will greatly reduce the formation of condensation in the first place.
 
wby0nder said:
I've been doing some research on this issue. Word is that OUTflow restriction is better than inflow restriction. Makes your heater work better and is less likely to screw up critical airflow over the cylinders. Oil sump and intake tube blankets may help but some report little difference. Wag Aero has them. I would talk to your engine manufacturer about your installation. They may have recomendations.
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Yeah, outflow restriction is what I'd had in mind, and what the guy in Crookston did for his. The heater needs all the help it can get...

The Tannis heater you have may already be doing a lot to minimize moisture build up in your engine. It may not get hot enough to boil off water but it will greatly reduce the formation of condensation in the first place.
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How so? I don't run my Tanis but for a few hours before I go fly. If I'm not flying that day, the airplane sits unheated.
 
How so? I don't run my Tanis but for a few hours before I go fly. If I'm not flying that day, the airplane sits unheated.[/quote]

Oh. In that case it wont help much. But it is very good for eliminating cold start damage.

Another idea is simply to drain the moisture out with the oil. It may not get it all but it can't hurt. Warm it up and drop the oil.

There are also crankcase dehumidifier/heater kits I've seen.
 
Remember that the C-series & 0-200 have an oil tank. unlike most other engines, the oil tankplug is at the very bottom of the tank.
 

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The typical O-200 installation has a channel of baffling from just under the crankshaft prop flange that directs cooling air along the bottom of the crankcase and spills it over the oil tank. Blocking off the entrance to this channel will raise oil temperature.

Restricting overall flow through the cowling can sometimes raise cylinder temps too much without raising oil temps enough. The bulb tank on small Continentals loses a lot of oil heat and the tank cover is a good place to start. Since I started running Aeroshell 15W50 in mine I can't get the temp up much and I need to buy or make that cover. Even in the summer the temp is rather low even though the CHTs are plenty high. Last summer I left the cooling channel cover in place and still had temps of 160 or less.

The oil temperature takeoff is in the oil screen downstream of the pump and is an indication of the oil's temp in the tank. Coming off the pistons and other mechanisms it will be hotter than the gauge says, before it runs along the bottom of the case and some of its heat is extracted. Even so, 140°F is a little too cool. The manufacturer specifies a max oil temp of the O-200 of 240°F (for detergent oils).

Make sure your gauge is telling the truth. Drop the probe into a can of boiling water and see that it says something close to 212°F.

Dan
 
wby0nder said:
The Tannis heater you have may already be doing a lot to minimize moisture build up in your engine. It may not get hot enough to boil off water but it will greatly reduce the formation of condensation in the first place.
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There's a lot of folks with the opposite opinion, i.e. engine sump and cylinder heaters may actually increase internal corrosion problems if left on continuously. IIRC even Tanis recommends that their products not be operated for extended periods.
 
lancefisher said:
There's a lot of folks with the opposite opinion, i.e. engine sump and cylinder heaters may actually increase internal corrosion problems if left on continuously. IIRC even Tanis recommends that their products not be operated for extended periods.
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Bob Reiff on a post at the red board
Reiff Preheat Systems said:
We have been encouraging Aviation Consumer for years to conduct a study on this issue. Now they have...

PREHEAT AND CORROSION: NO SMOKING GUN

Aviation Consumer, March 2007, pg. 23​

We can't print the article due to their copyright, but you can buy a copy off their web site. Here are a few excerpts:

They instrumented a Continental 520 on a Bonanza that was equipped with our Standard System. The preheat system was plugged in and they recorded internal crankcase temperature and %RH (relative humidity) data over a 7 day span. During that period ambient temps ranged from teens to 30F.

Results... The internal RH started at 60%RH at ambient temperature. After about 12 hrs of heating it stabilized at about 120F and 15%RH and it held pretty constant for 7 days.

Conclusion... "These findings don't support the view that preheaters cause corrosion."

"Clearly, a preheater seems to dry the engine out, not cause it to behave like a terrarium."

"While our experiment is far from definitive and doesn't consider all possible ambient conditions, it does seem to show that far from causing corrosion, an always-on preheater actually appears to benefit the engine."
__________________
Bob Reiff
Member AOPA, EAA
Reiff Preheat Systems
262 593 5292
www.ReiffPreheat.com
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http://forums.aopa.org/newreply.php?do=newreply&p=637152
 
smigaldi said:
Bob Reiff on a post at the red board


http://forums.aopa.org/newreply.php?do=newreply&p=637152
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Constant heat, if it's warm enough, will drive out the moisture. If it's not warm enough (small heater or really cold weather) it might just get warm enough to accelerate the chemical reactions between the water and oil and in the corrosion process itself. It might drive the water out of the oil only to have it condense on the cooler parts of the cylinders and case and actually make things worse.

And constant heat has its drawbacks. Rubber seals and hoses and gaskets age much faster when warm. The volatile compounds that make them flexible will evaporate faster and they'll go hard. This is a common problem in cars that have block heaters that circulate the coolant through the heater hoses: those hoses can harden up in a couple of years. And then they bust on a hot day when the system pressure gets high.

Tradeoffs everywhere. Things rot and fall apart whatever we do. We can only try to slow the process.

Dan
 
Dan Thomas said:
The typical O-200 installation has a channel of baffling from just under the crankshaft prop flange that directs cooling air along the bottom of the crankcase and spills it over the oil tank. Blocking off the entrance to this channel will raise oil temperature.
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For me, taping the inlets resulted in a 10-15 degree oil temperature increase, up to 160 and change. I will try the wag aero sump sack on Sunday.
 
GeorgeC said:
For me, taping the inlets resulted in a 10-15 degree oil temperature increase, up to 160 and change. I will try the wag aero sump sack on Sunday.
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160 is all I can get out of my c85, cousin to the 0-200 in my 140. I tape up first 1.5inches of the inboard intake grates and a blast tube in the baffle. I would try the sump bag but have an early 80s philips preheater that’s like a electric hot water heater element that’s now tied shape that wraps around the sump so I can’t really wrap it.

Our kidney tanks are an oil cooler in my mind. Out west in heat and elevation this summer lots of guys were running 220 and I was under 200
 
The whole boiling the water out of your oil is a bit of an old wives tale. For starters, the water will evaporate bellow boiling point. Second, as soon as you shut down you will be introducing water back into the oil with even the slightest bit of humidity.

If you want to raise the temp to help with lubricity that is one thing, don't do it to "boil off the water". As long as the oil temp is in the green on the gauge there should be no reason to change anything.
 
Grum.Man said:
The whole boiling the water out of your oil is a bit of an old wives tale. For starters, the water will evaporate bellow boiling point. Second, as soon as you shut down you will be introducing water back into the oil with even the slightest bit of humidity.

If you want to raise the temp to help with lubricity that is one thing, don't do it to "boil off the water". As long as the oil temp is in the green on the gauge there should be no reason to change anything.
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Doesn’t concept have some merit if we are discussing ground running only than flying for a bit?
 
In summer if I climb up high, my oil is going to be under 175F. I wouldn't worry about nice cool oil temps, the oil being too hot would be bothersome.
 
Huckster79 said:
Doesn’t concept have some merit if we are discussing ground running only than flying for a bit?
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The difference is in flight the rest of the engine is getting hot enough for long enough to aid the evaporation. A ground run only warms up the engine then you shut it down with hot moist air inside.
 
Grum.Man said:
The difference is in flight the rest of the engine is getting hot enough for long enough to aid the evaporation. A ground run only warms up the engine then you shut it down with hot moist air inside.
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Yes, that makes all the sense in the world...
 
My oil temp has always run on line between yellow and green. I have taped off the oil cooler with little change on the analog oil temp gauge. I plan to heat the temp sensor in a pan of oil at a known temperature and see what the gauge is reading.

At least that way I have an Idea of the oil temp as shown on the old analog gauge.
 
Huckster79 said:
Doesn’t concept have some merit if we are discussing ground running only than flying for a bit?
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On C-140’s there are two oblong holes in the cowling just below the prop. Factory aluminum covers were available to plug these two holes for winter flying in order to increase oil temps. Are you using these covers? These covers reduce the airflow along the bottom of the C-85 crankcase as previously referenced.

Isn’t the blast tube you reference covering going to the exhaust and then providing heat to the cabin? Covering this tube likely does not do much to oil temp but may impact cabin heat and your comfort.
 
There are three blast tubes; one for cabin heat, one for carb heat, and another that runs down to the oil screen.

I couldn't install the sump sack this weekend, as there's stuff rtv'd to the sump :mad:
 
You don't actually need to boil the condensation out; 140°F will eventually do it, it will just take longer. As others have suggested, keeping your oil warm at all times may prevent condensation (but not moisture from combustion) in the crankcase. And I don't know where your oil temp sensor resides; it may be in a spot where it gets colder than the actual crankcase.
 
Kenny Phillips said:
You don't actually need to boil the condensation out; 140°F will eventually do it, it will just take longer. As others have suggested, keeping your oil warm at all times may prevent condensation (but not moisture from combustion) in the crankcase. And I don't know where your oil temp sensor resides; it may be in a spot where it gets colder than the actual crankcase.
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Right. The vapor pressure of the water increases with temperature, so it evaporates faster. But running an engine too cool can mean that water accumulates faster than it's being driven out, and corrosion is the result. From https://www.lycoming.com/content/operating-cold-weather

...we read this:
Engine operating temperature is another item that is not usually given enough consideration in cold weather. We usually are very cautious about high oil temperature which we know is detrimental to good engine health, while a low oil temperature is easier to accept. The desired oil temperature range for Lycoming engines is from 165˚ to 220˚ F. If the aircraft has a winterization kit, it should be installed when operating in outside air temperatures (OAT) that are below the 40˚ to 45˚ F range. If no winterization kit is supplied and the engine is not equipped with a thermostatic bypass valve, it may be necessary to improvise a means of blocking off a portion of the airflow to the oil cooler. Keeping the oil temperature above the minimum recommended temperature is a factor in engine longevity. Low operating temperatures do not vaporize the moisture that collects in the oil as the engine breathes damp air for normal combustion. When minimum recommended oil temperatures are not maintained, oil should be changed more frequently than the normally recommended 50-hour change cycle. This is necessary in order to eliminate the moisture that collects and contaminates the oil.

"...the engine breathes damp air for normal combustion." A bad way of wording it. Cold air is dry. The moisture comes from the combustion process and as the rings leak a little of the combustion gases into the crankcase, moisture will accumulate there.
 
Kenny Phillips said:
And I don't know where your oil temp sensor resides; it may be in a spot where it gets colder than the actual crankcase.
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Small Continentals have the oil temp probe in the oil screen, immediately after the pump. Most engines have their probes in similar locations. The TCDS will specify oil inlet temperatures; oil coming out of the engine back to the sump will be warmer.
 
Briar Rabbit said:
On C-140’s there are two oblong holes in the cowling just below the prop. Factory aluminum covers were available to plug these two holes for winter flying in order to increase oil temps. Are you using these covers? These covers reduce the airflow along the bottom of the C-85 crankcase as previously referenced.

Isn’t the blast tube you reference covering going to the exhaust and then providing heat to the cabin? Covering this tube likely does not do much to oil temp but may impact cabin heat and your comfort.
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Its not the one out front, its the one on under the cowl on the baffold piece. The one you are speaking of it make sure is open.

GeorgeC said:
There are three blast tubes; one for cabin heat, one for carb heat, and another that runs down to the oil screen.

I couldn't install the sump sack this weekend, as there's stuff rtv'd to the sump :mad:
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That is why I can't use the sump sack... I would need to remove the preheater, and I'm not about to do that...
 
Well I tested the oil temp sender and it seems to be working fine. I put it in a can with hot water and grounded sender to firewall. Temp of water was 180F and my analog gauge was 1/2 way in the yellow of the gauge. So my guess is bottom of the green is around 200F.

Bottom of the green is a normal reading for my O-320 at 2500rpm straight and level flight..
 
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