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Oil Dipstick Heater


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#1 rangermb

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Posted 13 February 2012 - 10:09 PM

Has anyone tried one of these. It temporarily replaces the dipstick to put heat into the engine? I use an external heater now, but don't really want to glue a pad heater to the case.



#2 smccray

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Posted 13 February 2012 - 10:58 PM


Quote: rangermb


...but don't really want to glue a pad heater to the case.




Why?  I respect your decision, but I'd like to understand your concern.



#3 scottfromiowa

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Posted 13 February 2012 - 11:18 PM

Does it have a thermostat?  I had one and didn't care for it.  I have a block heater now with thermostat.  I prefer this in combination with a ceramic heater that I blow with heat duct into the cowl flap opening.



#4 rangermb

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Posted 13 February 2012 - 11:36 PM


Quote: smccray



Quote: rangermb


...but don't really want to glue a pad heater to the case.




Why?  I respect your decision, but I'd like to understand your concern.




I'm still a bit new to my plane and am still learning my way around under the cowl. I'm not too interested in making permanent changes yet. Maybe down the road, unless my work lets me transfer to some place warmer (I'm in NW Indiana).



#5 jetdriven

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Posted 14 February 2012 - 12:03 AM

I read somewhere they are not good to use.   Oil gets warm but cooks a little, and the engine stays cold.  The real purpose of preheat Is to warm the crank and case so the bearing clearances don't get too tight.  


 


IIRC lyciming does not recommend them either.  


 



#6 Piloto

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Posted 14 February 2012 - 12:53 AM

Automobile oil dip stick heaters are very popular in Canada. You see a lot of cars at night at the motels plug in. Besides their simplicity of use warming up the oil directly is more effective than blowing hot air from the outside. Before start you want to make sure the oil is ready to lubricate to avoid bearings wear. Also when you heat from inside the heat is better confined to the engine moving parts (cranckshaft, connecting rod and pistons) than to just cylinder heads when hot air is applied externally.


 


José



#7 Jeff_S

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Posted 14 February 2012 - 07:24 AM

As jetdriven has said, these oil dipstick heaters are a definite no-no for aircraft engine preheating. The tolerances in aircraft cylinders are much less than in a car because of the differential metals used, so the goal of engine preheating is not only to warm the oil but also to increase those tolerances back to normal levels and avoid damaging cylinders during a cold start. The oil dipstick method only heats the oil, so you're only solving half the problem (and with modern multi-viscosity oils, not even the most important half).



#8 animalmover

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Posted 14 February 2012 - 09:33 AM

A trouble light with a 100w bulb inserted in the cowl and a sleeping bag over the top does a good job. 



#9 Piloto

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Posted 14 February 2012 - 10:26 AM


Quote: Jeff_S


As jetdriven has said, these oil dipstick heaters are a definite no-no for aircraft engine preheating. The tolerances in aircraft cylinders are much less than in a car because of the differential metals used, so the goal of engine preheating is not only to warm the oil but also to increase those tolerances back to normal levels and avoid damaging cylinders during a cold start. The oil dipstick method only heats the oil, so you're only solving half the problem (and with modern multi-viscosity oils, not even the most important half).




 


I think there is a misunderstanding on the use of each device. The hot air blowers are typically 5,000 watts devices that are used for about 1/2 hour to heat up the engine quickly on the ramp. The dipstick heaters are 150 watts devices that are used for overnite heating in a hangar. At hangar temperatures of 20F i have seen cylinder temperatures of 60F the next day after having the dipstick all night in the engine. Using cowling plugs helps on keeping a uniform engine temperature. The advantages of the dipstick heater are its low cost, portability, easy of use and low power requirements. The drawback is the long time it takes to heat the engine. You need to have it plug in overnite the day before your trip.


At temperatures below 0F it is important that oil is in liquid form to assure that the oil pump can suck it and circulate at engine start. Otherwise it may take about a minute or more to get oil pressure. Greenland and northermn Canada bush pilots add a quart of AVGAS at night to the oil to lower its viscosity.


Unlike water cooled engines were the temperatures are more constant air cooled engines like those in airplanes are subject to a wider temperature range. To avoid cylinder damage (specially at low temperatures) the fit tolerances of cylinders to pistons/rings is less tight to allow for metal expansion and contraction. The drawback is the relative high oil consumption of air cooled engines vs water cooled engines. This is why you don't need to check the oil level on your car as often as in your plane.


José


 


 



#10 Shadrach

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Posted 14 February 2012 - 10:32 AM


Quote: rangermb


Has anyone tried one of these. It temporarily replaces the dipstick to put heat into the engine? I use an external heater now, but don't really want to glue a pad heater to the case.




I think they're a bad idea. I have seen them mealt the plastic dipstick tube. Forced air is my choice...



#11 jwilkins

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Posted 14 February 2012 - 12:02 PM


Quote: rangermb


Has anyone tried one of these. It temporarily replaces the dipstick to put heat into the engine? I use an external heater now, but don't really want to glue a pad heater to the case.




Gluing a pad heater is really not a big deal and is probably the best way to preheat the oil. If you are in a REALLY cold area the combination sump and cylinder band heaters are better. Cowl plugs and a quilted moving blanket over the cowl will help keep some of the heat in the cowl to better stabilize temperatures. The sump heater is an expense but a couple hours installation and the cost of the heater is a lot less than engine wear due to cold starting


Back East when the plane was reallly cold soaked (below zero) I would go the full Monty:


Sump and cylinder heaters on; cowl plugs in and the moving blanket over the cowl.


A small quartz heater in the cabin to warm up the radios and gyros


A hot air heater with aluminum dryer vent hose directed into the cowl flaps


Pre heat a quart of oil in boiling water, add it and then run the prop through several cycles.


I think one of the most important points is to NOT rush it. You want the temperatures in the engine to stabilize and that won't happen with a 30 minute preheat.


If the plane is in a hanger the sump and cylinder band heaters with a blanket do a good job. There has been a lot of fussing that using heaters might cause condensation. You get condensation when the metal is cold and the moisture condenses on that colder surface. Using a blanket with the sump and band heaters I found the entire engine would stay warm and saw no indication of condensation (checking the dip stick tube is a good area to look for warm moist air condensing on a cold surface).


I have no aircraft experience with the dip stick heaters but I don't really like the idea. I just seems too localized. Only the very end of the dip stick is submerged in oil and a dip stick heater is going to be putting heat out above the oil level.  Dependingon the OAT the low wattage heater in the dipstick may not be capable of delivering enough calories to warm up more than a very localized area, no matter how long it is on. If I didn't have any other options, I would personally prefer a forced air heater with flex ducts to put in the cowl flaps. With a blanket and cowl plugs it will heat up the engine, but it takes time.


Cold soaked oil is difficult to warm up. In Alaska it is common to take the oil inside at night and keep it warm to put back in the morning. There are reports about people who did not drain the oil who had globs of frozen oil floating around in what they thought was properly warmed oil. In at least one case it caused an engine failure.


Don't be in a hurry in cold weather.


 


 


 



#12 jetdriven

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Posted 14 February 2012 - 03:49 PM

From Lycoming SI1505:


 


The use of a heated dipstick is not approved because heat is not distributed throughout the engine, and concentrated heat may damage non-metal engine parts. Proper pre-heat requires a thorough decongealing of all oil.






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