Constant Preheat?

MBDiagMan

MBDiagMan

Final Approach
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Doc
A few months ago, during the holidays, I rigged up a preheater. It consists of a very small electric heater, with a funneled stovepipe connector wired to it, and then drier hose on that. I put the drier hose up under the bottom of the cowl with the heater itself out from under the aircraft and turn on the heater. It blows enough warm air on the oil pan to get the oil to 70 degrees or more on a 20 or 30 degree day within a few hours.

It is a 35 mile drive to the airport so I just started leaving the heater hose in place when I'm not there. Any time I get to the airport, the oil temp is ready to start.

After reading the recent oil thread, I started thinking that keeping it warm all the time, might be allowing the warm oil to drain off of areas like the camshaft and followers. It is an O200A Continenatal. A long time ago, someone on this forum said that the Lycoming requires the Shell 100 PLUS due to the high camshaft and that this oil will stick to the cam better so that it is not dry during cold starts, but the PLUS is not as necessary for a Continental.

It might be that since the oil is warm and ready to flow immediately upon start up, it makes up for any loss of oil that might be dripping away from components.

What say you?
 
First, as a disclaimer, I live in Central Florida. I have no experience with pre-heaters.

One thing I would wonder about is keeping the temp in the 70's seems like it might speed up corrosion. Generally, higher temps mean faster chemical reactions (which is what oxidation i.e. corrosion is). Several somebodies will be along momentarily to explain why I'm right and wrong.

John
 
MBDiagMan said:
A few months ago, during the holidays, I rigged up a preheater. It consists of a very small electric heater, with a funneled stovepipe connector wired to it, and then drier hose on that. I put the drier hose up under the bottom of the cowl with the heater itself out from under the aircraft and turn on the heater. It blows enough warm air on the oil pan to get the oil to 70 degrees or more on a 20 or 30 degree day within a few hours.

It is a 35 mile drive to the airport so I just started leaving the heater hose in place when I'm not there. Any time I get to the airport, the oil temp is ready to start.

After reading the recent oil thread, I started thinking that keeping it warm all the time, might be allowing the warm oil to drain off of areas like the camshaft and followers. It is an O200A Continenatal. A long time ago, someone on this forum said that the Lycoming requires the Shell 100 PLUS due to the high camshaft and that this oil will stick to the cam better so that it is not dry during cold starts, but the PLUS is not as necessary for a Continental.

It might be that since the oil is warm and ready to flow immediately upon start up, it makes up for any loss of oil that might be dripping away from components.

What say you?
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You live in Texas, what happens in the summer when the ambient temp is above 70 degrees, will you need to refrigerate the engine so that oil will stick? Of course not, don't worry about about it.
 
Excellent point John. I hadn't thought of it. Now that I do though, since the Summers here make for 100 degrees in the hangar for several months, it wouldn't be any worse than that, but that dog might not hunt. The cold might make for more moisture to allow the corrosion.

Great point for thought and discussion, thanks.
 
PaulS said:
You live in Texas, what happens in the summer when the ambient temp is above 70 degrees, will you need to refrigerate the engine so that oil will stick? Of course not, don't worry about about it.
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Yep, another good and logical point. Thanks.
 
As long as you're not letting it sit for more than a couple of weeks at a time, you should be fine. If it's going to be more than 30 days between flights, you should look into the TCM instructions for inactive engines.
 
Yep, you guys are all right. I'm so used to having something to worry about, when there's nothing on my mind, my dreams come up with something to fill the void.:)

Thanks for the responses.
 
MBDiagMan said:
Yep, you guys are all right. I'm so used to having something to worry about, when there's nothing on my mind, my dreams come up with something to fill the void.:)

Thanks for the responses.
Click to expand...

So you're not happy unless you're not happy?

:D
 
MBDiagMan said:
After reading the recent oil thread, I started thinking that keeping it warm all the time, might be allowing the warm oil to drain off of areas like the camshaft and followers. It is an O200A Continenatal. A long time ago, someone on this forum said that the Lycoming requires the Shell 100 PLUS due to the high camshaft and that this oil will stick to the cam better so that it is not dry during cold starts, but the PLUS is not as necessary for a Continental.
Click to expand...

0-200 has the cam below the crank, but that does not place the cam in the oil. this engine has an oil tank hung below the case and all the oil will drain to it leaving the case area dry.
The 0-200 does not have cam and lifter problems, as other engines do.

Like any other engines your cylinders will be your biggest worry.
 
Ron Levy said:
As long as you're not letting it sit for more than a couple of weeks at a time, you should be fine. If it's going to be more than 30 days between flights, you should look into the TCM instructions for inactive engines.
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Believe it or not, the biggest factor in engine internal corrosion is the area's humidity.
 
Engine corrosion question for the group. when the engine has collected water inside, what happens to it?

We know it is in there when we remove the filler cap and see steam coming out.

So what happens to it, if we do not allow it to escape?
 
MBDiagMan said:
Excellent point John. I hadn't thought of it. Now that I do though, since the Summers here make for 100 degrees in the hangar for several months, it wouldn't be any worse than that, but that dog might not hunt. The cold might make for more moisture to allow the corrosion.

Great point for thought and discussion, thanks.
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The moisture is the issue of concern...if you have ambient moisture.:rofl: It is a valid concern in the winter up there, and the best way to deal with the issue is get a cell phone switch (look in the classifieds here, there is a dude who sells them.) and call in and turn it on.
 
steingar said:
We put ours on a garden timer so it only comes on during the weekends.
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Is this a joke?

Have you read Ted's how to make your engine last thread?

Putting pre-heat on an automatic timer is one of the worst things you can do.
 
Tom-D said:
Engine corrosion question for the group. when the engine has collected water inside, what happens to it?

We know it is in there when we remove the filler cap and see steam coming out.

So what happens to it, if we do not allow it to escape?
Click to expand...

Well, it reacts with other byproducts of combustion to form sulfuric acid for one thing, probably a couple of others. The issue is will it keep collecting more water through changes in the weather?

The thing about keeping it constantly heated is you need to keep it constantly well heated, far from the modified dew point, then you have no problem.
 
Stewartb said:
Who to believe?
FYI


Source: http://www.tcmlink.com/pdf2/SIL03-1.pdf
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They have to write their warning in CYA-Dumbest Operator, fashion, so they use the worst case scenario per counsel. In general, it is not a good idea in my opinion not just from the corrosion, but also waste of energy, standpoint.

I think if I wanted to keep an engine warm, I would rig something to blow warm air up the breather tube and out the oil fill hole.
 
Tom-D said:
Engine corrosion question for the group. when the engine has collected water inside, what happens to it?

We know it is in there when we remove the filler cap and see steam coming out.

So what happens to it, if we do not allow it to escape?
Click to expand...

Answer from my own observations. It condenses into liquid in the cylinders. Some of the liquid drains into the sump and makes a white acidic goo that floats on top of the oil. Change your oil often if you're going to heat constantly. No secret to that advice.

Ever walk into a heated greenhouse in winter? The humidity is hard to miss. Imagine that inside your engine and it'll explain why so many Lycoming cams have corrosion. TCMs see cam failures, too, just not as many as Lycoming. A friend had a cam corrosion failure in an 0-470 a few years ago. Like most Alaskan pilots he doesn't fly much during winter so he started using Phillips Anti Rust fly-away oil full time during winter. Not a bad plan.
 
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Henning said:
Well, it reacts with other byproducts of combustion to form sulfuric acid for one thing, probably a couple of others. The issue is will it keep collecting more water through changes in the weather?

The thing about keeping it constantly heated is you need to keep it constantly well heated, far from the modified dew point, then you have no problem.
Click to expand...

Agreed.....

Mine stays plugged in 24/7 from Oct to May.. Every year..... Water is kept at 120f , oil is kept at 140f.... Absolutely NO problems for me...:no::nonod:
 
From watching the EAA webinars, they recommend against constant preheat. It will allow for moisture to escape the oil and condense on cooler parts of the engine that may not be as well heated. They claim this was from research from the engine preheat manufacturers, if I remember correctly. I was convinced it was not a great idea to preheat all the time, and similarly, that it is a bad idea to start the engine for a few minutes on the ground if you haven't flown in a while, if you aren't going to fly.

They recommended opening the oil filler cap after a flight to allow some of the moist warm air to escape, as long as that doesn't create a condition in which you forget to put the cap back on later.

One of the best ways to fight corrosion I've heard of is to make a closed loop desiccant dryer. An inlet into the oil filler, and a return from the breather tube. One guy used a fishtank bubbler connected to some desiccant drying beads. I think Aircraft Spruce sells an open system, but in my mind you would have to regenerate the beads too often.

I like the EAA videos. They seemingly use science and research to explain things, instead of old wives tales (pilot tales?) of things to do for your plane.
 
What's the difference between pre-heating to 70 degrees or a plane in Florida that stays that temp year 'round?

Edit: Assuming the whole case, etc is at 70 degrees. I don't think the oil is at a point where the viscosity is low enough to remove it from all surfaces.
 
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Fearless Tower said:
Is this a joke?

Have you read Ted's how to make your engine last thread?

Putting pre-heat on an automatic timer is one of the worst things you can do.
Click to expand...

No, not flying the aircraft is the worst thing I can do. Without the engine heater I won't be flying a whole lot through midwestern winters. I would rather have a cellphone remote hooked up to the thing but haven't the requisite electronics expertise to obtain and install one.
 
I leave the rental 172 plugged in 24x7 all winter. That said, it does fly almost every day.
 
Stewartb said:
Answer from my own observations. It condenses into liquid in the cylinders. Some of the liquid drains into the sump and makes a white acidic goo that floats on top of the oil. Change your oil often if you're going to heat constantly. No secret to that advice.

Ever walk into a heated greenhouse in winter? The humidity is hard to miss. Imagine that inside your engine and it'll explain why so many Lycoming cams have corrosion. TCMs see cam failures, too, just not as many as Lycoming. A friend had a cam corrosion failure in an 0-470 a few years ago. Like most Alaskan pilots he doesn't fly much during winter so he started using Phillips Anti Rust fly-away oil full time during winter. Not a bad plan.
Click to expand...
Which has the greater specific gravity oil or water?
would the water be on top of the oil or will it sink to the bottom ?
As the engine cools the humidity will condense into water on all surfaces that are above the oil level. In the cylinders it will form below the pistons, yet we see the corrosion in the combustion chamber above the piston. WHY?
 
guardrail said:
What's the difference between pre-heating to 70 degrees or a plane in Florida that stays that temp year 'round?
Click to expand...
With constant temps, you have no breathing of the engine, as the air expands and contracts.
 
jsstevens said:
First, as a disclaimer, I live in Central Florida. I have no experience with pre-heaters.

One thing I would wonder about is keeping the temp in the 70's seems like it might speed up corrosion. Generally, higher temps mean faster chemical reactions (which is what oxidation i.e. corrosion is). Several somebodies will be along momentarily to explain why I'm right and wrong.

John
Click to expand...

Generally higher temp areas have a higher humidity content in the air. Cold areas not so much. So yes corrosion is more active in warm areas.
The desert being the exception.
 
Tom-D said:
Which has the greater specific gravity oil or water?
would the water be on top of the oil or will it sink to the bottom ?
As the engine cools the humidity will condense into water on all surfaces that are above the oil level. In the cylinders it will form below the pistons, yet we see the corrosion in the combustion chamber above the piston. WHY?
Click to expand...

Vapor pressure of the oil in the crankcase displaces the oxygen required for corrosion. The water in the crank case mixing with combustion byproducts suspended in the oil as it makes its way through is why oil sumps corrode through.
 
Henning said:
Yeah, you are not going to experience any negative issues operating like that.
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Yeap, they basically last forever if flown. It's been flown like that since it was overhauled. 400 over TBO now, compressions perfect, runs great, no oil leaks, and uses essentially no oil.
 
Henning said:
Yeah, you are not going to experience any negative issues operating like that.
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Yeap, they basically last forever if flown. It's been flown like that since it was overhauled. 400 over TBO now, compressions perfect, runs great, no oil leaks, and uses essentially no oil.

O-320-E2D
 
jesse said:
Yeap, they basically last forever if flown. It's been flown like that since it was overhauled. 400 over TBO now, compressions perfect, runs great, no oil leaks, and uses essentially no oil.

O-320-E2D
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Where the problems begin is when the plane sits through several weather fronts between cold weather operations, especially if there is significant taxi time before shut down. You run every day and you keep everything boiled out and polished up, no worries.
 
From my chemistry prof - Every 18 degF temperature increase doubles a corrosion rate. And every 18 degF doubles the potential absolute humidity of air (i. the amount of water potentially evaporable into the air). Water condenses at 100 percent humidity, and the dew point of combustion products is 180 degF. There will be combustion products (steam and CO2) and very little air in the crankcase of an operating engine.

Personally I like the idea of venting a crankcase as soon as possible after shutdown. I goose an engine on shutdown to purge the cylinders. But i don't worry about winter corrosion on a cold MN engine.
 
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I hated math classes. If it wasn't for pretty girls I would've never gone. So here's a question. Every 18*f increase doubles corrosion beginning where? Absolute zero? Zero? Freezing? Not being a smart-ass, I really appreciate the reference.
 
This has been a question for years. Why risk a high dollar engine. By a switch box for $300. Spend $30 per year and turn it on when your going to fly. It too easy
 
Henning said:
Vapor pressure of the oil in the crankcase displaces the oxygen required for corrosion. The water in the crank case mixing with combustion byproducts suspended in the oil as it makes its way through is why oil sumps corrode through.
Click to expand...

Total BS. the water will separate, settle to the bottom, as proven by the 0-300 sump corrosion problems.

The combustion bi-products will become sludge and settle to the bottom of the oil. but still on top of the water.
 
Stewartb said:
I hated math classes. If it wasn't for pretty girls I would've never gone. So here's a question. Every 18*f increase doubles corrosion beginning where? Absolute zero? Zero? Freezing? Not being a smart-ass, I really appreciate the reference.
Click to expand...
Check a psychometric chart in a heating and ventilating Mechanical Engineering text. It is amazing how close the humidity stuff checks to the doubling every 18 degF "rule". Obviously it doesn't go all the way to zero (after all doubling zero is still zero). But most car corrosion and airplane I assume happens during the summer from salt etc from the previous winter.

The chemistry rate thing was from class 55 years ago. I've seen it elsewhere too.

Back then there were no pretty girls in math...........:yikes:
 
Tom-D said:
Total BS. the water will separate, settle to the bottom, as proven by the 0-300 sump corrosion problems.

The combustion bi-products will become sludge and settle to the bottom of the oil. but still on top of the water.
Click to expand...

The water becomes acidic as well, that was my point, that is where it does most of the damage, in the pan under the oil.
 
nrpetersen said:
Check a psychometric chart in a heating and ventilating Mechanical Engineering text. It is amazing how close the humidity stuff checks to the doubling every 18 degF "rule". Obviously it doesn't go all the way to zero (after all doubling zero is still zero).
Click to expand...
Here's the NOAA calculator for the saturated vapor pressure of water as a function of temperature. It also gives an empirical formula that I used to see if that rule of thumb really holds. It kind of makes sense that it might because the formula is exponential, but actually it only really works well for temperatures below freezing, and is closest to being accurate right around -40. Up around the boiling point it's pretty far off.

(The formula uses T in degrees C -- 18 dF == 10 degrees C.)
 
Henning said:
The water becomes acidic as well,
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Well, I certainly wouldn't drink it, But I'm no chemist, to tell you what is in it.

Try this, add equal parts water, liquid soap, and engine oil. shake it until it turns milky. set it in a warm window and see what happens. you'll understand what happens in your engine after the water reaches the oil sump.
 
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