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Engine oil heater question

Tankerpilot75

Well Known Member
Last year I installed a Reiff Oil Heater on my IO-360. Of course the winter this year is warmer than normal it seems. However my question is the same. Should the sump heater be left plugged in when left in the hangar using the Reiff thermostat to regulate oil temperature? What are the pros and cons?

I?ve discussed this question with several pilots at my airport and their responses go both ways. I?ve noticed when it?s left plugged in with full time power the oil is consistently warm (not hot) and the engine compartment feels around 60 to 65 degrees. When I use a wall plug purchased from Ace Hardware that activates only when ambient temperatures drops below 35 degrees, I?ve noticed the oil temperature is significantly lower and the engine compartment reflects ambient temperatures. I assume the temperature controlled wall plug results in more temperature cycles than just leaving it powered full time (therefore I assume greater potential for moisture from condensation).

Wifi activated control is not an option. No cellular access in hangar areas and very poor access at airport.
 
Do a search, there should be some lengthy discussions on this topic.

I would never leave sump heaters on, with or without a remote temperature controller. The heaters do exactly what they say, heat the sump. The now warm oil will give off whatever moisture it may have and that moisture will plate out on the cold engine parts, like your cam. If you don?t soon run the engine the moisture will do what it does. Not what you want.

If you also have the ring cylinder heating elements this problem is mitigated somewhat, but not enough for me.

The standard process is to get to the hangar a little early, plug in the heaters, do all the stuff you need, go get a cup of coffee, then come back and fly.

Carl
 
Crazy simple and cheap

$18 Walmart heater, 4x6 floor HVAC vent, aluminum tape, rigid/flex ducting 4”, timer and extension cord. I set timer to come on at 5am, show up at airport at 7am...oil and chts 60 +.

 
As long as you're using multi-grade oil and it's not Minnesota cold out, you shouldn't have a problem with the oil flowing well at start up. IMO, the issue is more of a cylinder temp issue because of the potential of scuffing at start up. I'd hypothesize that you could leave cylinder band heaters on full time (with no sump heat on) and address much of the cold start issue while avoiding the condensation problem. Just a hypothesis though.
 
Think of a cold glass of water on a warm summer day. Moisture collects on the outside of the cold glass.

Dis-similar temps will result in the engine when you plug in your engine heater. Warmer temps will be near the heat source, colder temps will exist further out. If the heat is left on all winter, then places where the temp/dew point match in the engine are susceptible to collecting moisture like your glass of water all winter long and rust.

A metal prop is a cold sink and will cause the front of the crank to be cold. A constant speed prop may get moisture collecting in its hub.

So these are problems to over come or turn it on before flight. There are solutions to turn on the pre-heater via a cell phone connection before going to the airport.
 
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As long as you're using multi-grade oil and it's not Minnesota cold out, you shouldn't have a problem with the oil flowing well at start up. IMO, the issue is more of a cylinder temp issue because of the potential of scuffing at start up. I'd hypothesize that you could leave cylinder band heaters on full time (with no sump heat on) and address much of the cold start issue while avoiding the condensation problem. Just a hypothesis though.

I recall a recent discussion (Superior webinar maybe) regarding the cylinder band heaters causing rust to appear in a ring shape internally on the cylinders. No indications of short or extended usage, but just an observation.
 
I spoke to Allen Barrett about leaving an engine heater on all the time and he absolutely not. As pointed out above, they cause condensation, which causes internal rust.

Can you get to the hangar early, turn on your heater, and go for breakfast while your engine warms up?

See this Lycoming document for cold weather operations.

That Lycoming document states:
Lycoming said:
... For most Lycoming models, preheat should be applied anytime temperatures are at 10˚ F or lower. The exception to this rule is the 76 series models that include the O-320-H, and the O/LO-360-E. These engines should be preheated when temperatures are below 20˚ F...
 
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I'll plug mine in the night before sometimes, but don't just leave it on all the time.
 
My sump heater runs 24/7 four months of the year, CHT and oil temps above 80*F all the time....the RV thinks it is in Florida for the winter. Nineteen years since overhaul on the heater, no signs of rust.
 
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Think of a cold glass of water on a warm summer day. Moisture collects on the outside of the cold glass.

Dis-similar temps will result in the engine when you plug in your engine heater. Warmer temps will be near the heat source, colder temps will exist further out. If the heat is left on all winter, then places where the temp/dew point match in the engine are susceptible to collecting moisture like your glass of water all winter long and rust.

A metal prop is a cold sink and will cause the front of the crank to be cold. A constant speed prop may get moisture collecting in its hub.

So these are problems to over come or turn it on before flight. There are solutions to turn on the pre-heater via a cell phone connection before going to the airport.


A sump heater heats the oil first and the air inside the engine second, along with other non-submersed parts. Air outside the engine is irrelevant. That leaves the air temp approximately the same as the steel part temps. The air inside the engine heats along with the engine, keeping the dew points aligned and the risk of condensation minimal. The crankcase is the exception, where outside air exposure can make it colder than the internal engine air. However, condensation on the crankcase is of no concern, from a corrosion perspective, as it is aluminum. Any condensation developed on the inside of the case will drip down to the oil pan, where it does no short term damage. I believe you get much more condensation inside the engine after hot shut down then produced from a sump heater. The 200* air inside your engine holds a LOT of moisture and as that air cools down, that moisture must precipitate out as the saturation level shrinks with the cooling temps. Same concept that creates dew on the grass in the early morning.

My experience is that the sump heater uniformly heats the engine and cowl interior assuming plugs and blanket are used, with the exception of the oil itself, being the heat source. No cold air sources to create temp differentials and condensation. I am in Chicago and do a lot of winter flying.

I would never use the cyl bands for more than a couple hours. The intense heat at the band contact area will eventually burn off any oil there, allowing corrossion in that spot. I am not surprised that some find rust bands inside the cyl aligned with the heaters.

Larry
 
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These answers and rational are exactly the same I hear at my airport. Again opinions and justification seem to land on both sides of the original question. Oh well, so be it.
 
I had an Aerostar that had a corrosion problem until I put a Tanis pre-heat on it. Both oil sump and cylinders. Left it plugged in continuously in the winter at Tanis's recommendation. The very important thing to do is remove the oil filler cap. This allows any moisture escape through the tube. I did this summer and winter immediately after last landing of the day with or without using the pre-heat.
 
On a side bar, but not completely off topic . . . I have been doing some experiments and calculations for improving the typical crankcase dryer. It is all about dew point temperature. The best I can figure the crankcase dew point at shutdown is around 180F. If it is winter, the ambient dew point is pretty low.

OK, finally the experiment. I took a 12vdc coleman mattress inflator and hooked to my oil filler (IO360) with 10" of 1/4" ID hose and a stopper. It completely replaced the crankcase air in 3 min as confirmed by the exit air dew point being within 1-2 C of the ambient dew point. The main variable is the crummy meter I use to measure humidity. It takes 5 min for a 540.

If this was done at shutdown, there is little chance (probably an understatement) any region of the engine will be close to the dew point. 3 or 5 min is not very long and easy to do during normal post flight activities.

This can put any corrosion worries to rest for leaving a (self regulated) heater on for extended periods. Not sure about other reasons, but that one can be addressed.

I use a phone switch or turn on the night before. A hand in the cooling inlets will find the plenum cavity toasty warm. No way it will have any part below dew point.

But wait, there is more. After the purge (as I call it), a 2 l/min flow will achieve the lowest dew point ( in the crankcase) possible with silica gel in 45 min. Then the dryer can be shut off. Recirculation is not needed and 45 min of drying ambient air will collect less water than a recirculating system that does not use a purge. The desiccant will last quite a while this way before it needs regeneration.

Back to the Op's question . . .
 
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Rebuild Necessary

I had a PA23 Apache once. Had both engines zero timed when I bought it. Had it for 8 years here in NH. Installed heating pads on both engines and ran them all during the winter. By year three I ended up paying for tear downs and replacement of cams and lifters as a result of corrosion caused from the freezing hangar temps and moisture. Never again. The heating pad on my RV9 only goes on just before flying.
 
I've never understood why cylinder band heaters should cause corrosion inside a cylinder. Surely if the cylinder wall gets hot enough to boil off the oil (>500?F) they will also boil off any water?

Back when I was in a flying club we had three planes that lived in a large unheated hangar. The sump heaters were kept plugged in continuously for months at a time, yet the engines always made TBO or beyond.
 
I've never understood why cylinder band heaters should cause corrosion inside a cylinder. Surely if the cylinder wall gets hot enough to boil off the oil (>500?F) they will also boil off any water?

Back when I was in a flying club we had three planes that lived in a large unheated hangar. The sump heaters were kept plugged in continuously for months at a time, yet the engines always made TBO or beyond.

Heat is a conundrum in aircraft engines.

On the plus side, heat evaporates moisture and reduces the relative humidity inside the case.

On the downside, it heats the oil and allows the oil film on internal parts to flow off of the parts faster. Also, if moisture (or other corrosive products) are present, heat speeds the rusting process.

There's plenty of anecdotal evidence that heating the engine over the long term is bad, and there are just as many anecdotes which show heating the engine is good.
 
a lot of posts about condensation causing rust. i think everyone has seen something rust that you know was never exposed to liquid water. i think i read somewhere that above 65% rel. hum. this becomes a possibility.
after reading a lot of threads about this subject there is a lot of anecdotal info but not much scientific fact for most of it. i have my opinions but it seems everyone has got one and we don't really know what's going on in our engines.
for ex. i have never seen a graph, statistics that show at what point the higher temps.[which cause increased rates of chemical reactions-rust] is offset by lowered rel. humidity because of rise in temp. isn't that what's it's all about?
 
If I had time to `get there early` to turn on a heater, I would not need a sump heater in the first place. The sun would be out and the temps usually above freezing by then.

When I get home Friday, the bird gets plugged in for Monday AM departure. If weather is bad, I drive the commute and the engine stays heated until the next Monday.

Like Larry said, the whole cowl interior is warmed. There is no temp differential to create an imagined condensation point.
 
A lot of the conventional wisdom on this topic seems to rely on speculation rather than actual data. Here's an exception:

http://www.reiffpreheat.com/Article-Fiorentini-ContinuousPreheating.pdf

This author found that relative humidity inside the crankcase of a heated engine is considerably lower than that outside (ambient). This suggests that leaving the oil heater on subjects the engine to conditions not unlike a summer day in Phoenix (assuming use of a blanket and with oil filler open).
 
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Again VAF?s collective wisdom is great

I?ve learned a lot from the different opinions/wisdom/articles presented here on this subject. So what am I going to do?

1. Leave the Reiff heater plugged in for the rest of the winter season.
2. Loosen/remove the oil cap so moisture can vent from the engine (something I wasn?t doing before).
3. Cover the engine compartment to help the heat be retained so a more uniform /higher temperature level will be maintained.


Again thanks for everyone?s imput.
 
I’ve learned a lot from the different opinions/wisdom/articles presented here on this subject. So what am I going to do?

1. Leave the Reiff heater plugged in for the rest of the winter season.
2. Loosen/remove the oil cap so moisture can vent from the engine (something I wasn’t doing before).
3. Cover the engine compartment to help the heat be retained so a more uniform /higher temperature level will be maintained.


Again thanks for everyone’s imput.

A couple more tips for continuous heating:

Plug the cowl openings behind the prop and

Fly your plane often. :)
 
Engine dryer - black max

Ken Sutton of the Twin Cessna Flyer association did a comprehensive study of pre-heating, which pointed to the need for dehydration.
Lots of imperial data.
http://nebula.wsimg.com/1fd3c69cbb2...3181A996A1861998A&disposition=0&alloworigin=1

I'm always impressed with someone when they validate what I've already done! :D



KenSutton said:
Summary:
So what have I learned from all of my efforts that will help me better manage the engine health of my C-310? Going forward I plan to:
? Preheat the engines before every flight in an attempt to get their temperature as close as possible to normal operating temperature. The GSM Auto cellular switch goes a long way to providing convenient and timely control to the engine preheating process.
? Use engine dehydrators when preheating to reduce the relative humidity and lower the dew point inside the engines.
? Use insulated engine cowl covers to increase effectiveness of preheating, and to more uniformly preheat all the engine components.
? Within 30-minutes of engine shutdown, begin using engine dehydrators to rapidly reduce the relative humidity inside the engines. Continue to run the dehydrators on the engines until the next time the engines are ready to be started. This will maintain a very low relative humidity environment inside the engines, protecting them from rust and corrosion even after the oil coating on those components has dripped back into the sump.
? Use an engine oil that contains an anti-corrosion additive, or use an anti-corrosion additive in the engine oil.
 
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