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Pre-Heat on Marginal Days

Fishsticks

Registered User
Currently I’m using a Reiff Preheater connected to a remote switch in the hangar. I check the weather the night before flying and if it looks good I turn the preheat on. I’ve read that cycling the preheater encourages condensation build up within the crankcase as you never get the engine hot enough to boil the water out of the oil. While I’ve been getting some fun flying in this winter I keep missing out on good flying days where the forecast indicates marginal the night before and then its totally flyable. Finding the intersection of work and weather has been frustrating and I’m looking for someone to tell me I’m overthinking it. I’m located at sea level on an airport right on salt water.

Pic of the ol bag of bolts wrapped in a blanket. While it seems silly in a hangar the blanket makes a massive difference in preheat time and makes my gyros work when its in the teens…

Is preheating and then turning the preheater off really that big of a deal?

Should I just leave the preheater on until I go fly again?

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Put a drop light with a100w bulb inside the cowl and leave it on. It will keep it between 40 and 70F

Glenn
 
Personally, and I have no empirical data to prove it, it seems logical to me to leave a heating system plugged in constantly, rather than heating, cooling, etc. Remember, if that engine temp stays right at XX degrees, it's logical that condensation would be a one time effect. I always pull the dipstick out, and hang it on it's filler to permit the case to vent in any case, but again, I have no idea whether that really does any good.

I do know that in Fairbanks, one of our C-185s stayed plugged in, outdoors with an insulated engine cover, all winter. That airplane flew very infrequently, and I always wondered whether that constant heat was good or bad for the engine. Some time later, I was assigned that same aircraft, with the same engine. Engine ran fine, and went to TBO. That said, Fairbanks air in winter is about as dry as is possible, quite unlike being in a coastal area.

But, me, I'd just plug it in, keep it heated, go fly, and plug it in when you return.

MTV
 
Put a drop light with a100w bulb inside the cowl and leave it on. It will keep it between 40 and 70F

I used to use a 125W heat bulb with my last two planes, but it doesn't fit up into the cowl flaps on my 180.
I recently came up with this, works great.
Screws into a light bulb socket, which I have clamped to a strap & slide up under the oil sump.

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If you have a remote switch, bands, a sump pad and an engine blanket it should only take 2 hours or less to get the engine warm. Don't turn it on until after you check weather in the morning. What kind of temps are you talking about? What engine.
DENNY
 
DENNY - O300. Teens to above freezing. You've brought up a great point. I don't actually know how long it takes to preheat my engine. I've never turned the heater on and checked every couple of hours. I will get the temp gun out and do some testing! My engine is currently warmer when I start it in January than when it gets started in the summer... I like to fly before work so from just before sunrise till 8am or so, thus my focus on preheating before bed and going flying the next day.

Hotrod & cubdriver - With the lightbulb/100W heating element I'm concerned that it will make my airplane a mouse magnet. Nothing quite like a nice warm dry 170B to build a house inside!

MTV - Should I be pulling the dipstick out/opening the oil filler? I have never heard of doing that. (But i'm green as can be). It does make sense that leaving everything on would make the situation better not worse.
 
MTV - Should I be pulling the dipstick out/opening the oil filler? I have never heard of doing that. (But i'm green as can be). It does make sense that leaving everything on would make the situation better not worse.
I would think that leaving the oil cap or dipstick open while the heat is on would allow the moisture to escape. Like heating a pot of water on a stove, you can see the moisture rising until there is no more water in the pot. Leaving the caps on would trap the moisture inside where it does it's dirty deed.
 
I would think that leaving the oil cap or dipstick open while the heat is on would allow the moisture to escape. Like heating a pot of water on a stove, you can see the moisture rising until there is no more water in the pot. Leaving the caps on would trap the moisture inside where it does its up.dirty deed.

Yup.

MTV
 
Other than condensation, the colder it is the slower the corrosion... I just preheat if its colder than freezing. Of course leaving the heat on if the oil and air is dry will not do anything other than the oil eating the bearings after decades. But why risk a fire or something else happening? Of course I am in a dry area of AK where we can leave old diesels sit 20 years, pull them apart with no rust. Left an O360 for 12 years, no pickling, pulled it apart, cam was like new, zero rust on anything other than light surface flash rust on the cylinders that a scotchbrite cleaned right up. I would say the weather and climate is your biggest enemy. Next time you go fly, pop your oil cap off and watch the steam boil out of the case if you have any moisture in the oil that did not get ejected out the breather. Remember a byproduct of combustion is water. Even small amounts of blowby will allow a new supply of moisture into the case over time. Thats a habit an oldtimer showed us. Allows the trapped humidity of any to escape before allowing the engine to cool enough to let it condensate. Makes sense to me.
 
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