OIL COOLERS
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OIL COOLERS
Does the oil cooler have a thermostat internally ? If so which end ? My oil cooler is mounted vertically at the rear top left side of the engine on the back baffle.
So if I drain the oil from the sump, does it drain out of the oil cooler as well ?
The reason I ask is that over the ten years I have had my aircraft, I have noticed that the oil temp has gone up. Not with the outside summer heat but in general also in the winter. The yellow arch starts at 180 and it is often above that but well below the red line. The aircraft is very tightly cowled, so in the winter it is a juggling act to keep the CHT cool on the ground before the oil warms up, in the climb the CHT is quite high, but once in cruise the CHT is OK. The oil I use is Shell multigrade 15/50.
So if I drain the oil from the sump, does it drain out of the oil cooler as well ?
The reason I ask is that over the ten years I have had my aircraft, I have noticed that the oil temp has gone up. Not with the outside summer heat but in general also in the winter. The yellow arch starts at 180 and it is often above that but well below the red line. The aircraft is very tightly cowled, so in the winter it is a juggling act to keep the CHT cool on the ground before the oil warms up, in the climb the CHT is quite high, but once in cruise the CHT is OK. The oil I use is Shell multigrade 15/50.
What type of aircraft? What engine?
For one example: my Rotax 912 has no oil thermostat but I plan to install one. And when changing oil, one is heartily recommended to NOT drain the last drip.
For one example: my Rotax 912 has no oil thermostat but I plan to install one. And when changing oil, one is heartily recommended to NOT drain the last drip.
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Oil Thermostat
Lycoming engines usualy have a thermostat (usualy refered to as a vernatherm) installed in the housing the spin on oil filter fits to.
It is set to regulate the oil temperature to 180F, this is the temperature that Lycoming recomend to boil off the contaminates that are the cause of most internal corrosion.
Lycoming also recomend that you check the oil temperature system by putting the oil temp probe into a can of engine oil, heat the can and with a calibrated thermometer check the readings on the aircraft gauge.
As you might think The 180F mark is critical for engine health.
It is set to regulate the oil temperature to 180F, this is the temperature that Lycoming recomend to boil off the contaminates that are the cause of most internal corrosion.
Lycoming also recomend that you check the oil temperature system by putting the oil temp probe into a can of engine oil, heat the can and with a calibrated thermometer check the readings on the aircraft gauge.
As you might think The 180F mark is critical for engine health.
Last edited by A and C; 22nd Jul 2015 at 06:39.
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What are the cyl head temps getting to, hope it is not above 380f.
Lycoming 360 is always one rev away from failure, crap engine.
Oil needs to be above 180 but not over red line for health oil.
If to hot maybe an oil cooler flush may help.
Lycoming 360 is always one rev away from failure, crap engine.
Oil needs to be above 180 but not over red line for health oil.
If to hot maybe an oil cooler flush may help.
There is no thermostat in the cooler. As already mentioned there is a vernatherm which controls oil temperature.
When you drain the oil there may be some oil still left in the cooler, just like there is always oil left on the filter. I don't think this causes any issues as that oil is being pumped through the system when the engine is running.
However oil coolers do need flushing (cleaning) from to time. Perhaps it is clogged.
In general terms there are three possible causes for higher indicated oil temps. Clogged or partially clogged cooler, faulty vernatherm or faulty sensor.
If it's well below the red line I wouldn't panic too much at this stage.
From reading about your high CHT's one other area to look at is your baffling. If the baffling isn't snug and tight at the edges air will be leaking past the baffles. This is air that would have gone through the cooler or past the cooling fins on the heads. This could cause higher oil temp and more likely higher CHT's.
Provided the cowling has been designed properly and has good baffling tight cowling shouldn't be a problem. However poor fitting baffles and or badly worn baffle rubbers can be a problem.
What a lot of BS. The Lycoming 360 is a very good engine. Perhaps you're getting confused with the Continental IO360?
When you drain the oil there may be some oil still left in the cooler, just like there is always oil left on the filter. I don't think this causes any issues as that oil is being pumped through the system when the engine is running.
However oil coolers do need flushing (cleaning) from to time. Perhaps it is clogged.
In general terms there are three possible causes for higher indicated oil temps. Clogged or partially clogged cooler, faulty vernatherm or faulty sensor.
If it's well below the red line I wouldn't panic too much at this stage.
From reading about your high CHT's one other area to look at is your baffling. If the baffling isn't snug and tight at the edges air will be leaking past the baffles. This is air that would have gone through the cooler or past the cooling fins on the heads. This could cause higher oil temp and more likely higher CHT's.
Provided the cowling has been designed properly and has good baffling tight cowling shouldn't be a problem. However poor fitting baffles and or badly worn baffle rubbers can be a problem.
horizon flyer: Lycoming 360 is always one rev away from failure, crap engine.
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We had a similar problem with our Lycoming IO360, albeit over a shorter timescale.
Oil filter OK, no metal.
Oil temp sensor tested OK, Dial in A/c reading correctly.
Engineer found the coil spring on the Vernatherm valve in the oil cooling circuit had distorted badly.
New Vernatherm valve: problem sorted instantly.
Cusco
Oil filter OK, no metal.
Oil temp sensor tested OK, Dial in A/c reading correctly.
Engineer found the coil spring on the Vernatherm valve in the oil cooling circuit had distorted badly.
New Vernatherm valve: problem sorted instantly.
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No, my experiences of the Lycoming 360 series is a collection of design faults running in close formation ready to fail at any time and general do.
Agree about the baffling, very sensitive to baffling faults. Shaving the cooling fins off one side of the cylinder barrel is not very clever and effects cooling and the cylinder expand oval.
Vernatherms do fail worth checking as suggested.
Do you have a 4 channel engine monitor, always a good idea on a Ly360 to see what's cooking.
Have you had any sticking valves yet? if not you will.
Agree about the baffling, very sensitive to baffling faults. Shaving the cooling fins off one side of the cylinder barrel is not very clever and effects cooling and the cylinder expand oval.
Vernatherms do fail worth checking as suggested.
Do you have a 4 channel engine monitor, always a good idea on a Ly360 to see what's cooking.
Have you had any sticking valves yet? if not you will.
The flying school I used to help out at has regulatory authority to run their C 172 S models to 3500 hrs before overhaul. Every engine has made it to date despite the stresses and strains put on the engine by a constant diet of flight training.
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Horizon Flyer
I like Big Pistons do not hold your opinion, since the introduction of the later valve guides ( a lot of years back ) I have not seen a stuck valve in a fixed wing aircraft.
If you are cooking cylinders I would think you are asking too much power from the engine or your instrumentation or cooling is at fault.
Back in the 1970,s a well known flying school at Oxford ran its O-360's bottom end for 4000 hours before overhaul while changing the cylinders at 100 hours.
Most of the problems with light aircraft engines are as a result of under use.
Where do your CHT numbers come from ? I was looking the numbers for the O-235 this week and it said 400F for best engine life, 435F for continuous operation with an never excced of 500F, is the O-360 so diferent from the O-235 ?
If you are cooking cylinders I would think you are asking too much power from the engine or your instrumentation or cooling is at fault.
Back in the 1970,s a well known flying school at Oxford ran its O-360's bottom end for 4000 hours before overhaul while changing the cylinders at 100 hours.
Most of the problems with light aircraft engines are as a result of under use.
Where do your CHT numbers come from ? I was looking the numbers for the O-235 this week and it said 400F for best engine life, 435F for continuous operation with an never excced of 500F, is the O-360 so diferent from the O-235 ?
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Thank you for all the replies. I think I will check the spring and back flush the cooler. The baffling looks ok but I will try to seal a bit more. The reason I was more concerned at this point, is that at the end of August I am taking the RV6 to S France for two weeks, where currently it is +30c !! There are no cowl flaps and the inlet at the front is quite small compared to a Piper or Cessna.
In respect of the comments about the Lycoming 0-360. I also always thought this was one of the toughest versions. We used to have a Comanche 260 with the IO-540, which I believe has the same cylinders apart from the injection ports and of course 6 rather than 4 cylinders. We never had any problems apart from usual wear and in fact the bottom end had done 3300 hours on the original engine when we sold it.
In respect of the comments about the Lycoming 0-360. I also always thought this was one of the toughest versions. We used to have a Comanche 260 with the IO-540, which I believe has the same cylinders apart from the injection ports and of course 6 rather than 4 cylinders. We never had any problems apart from usual wear and in fact the bottom end had done 3300 hours on the original engine when we sold it.
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The reason I was more concerned at this point, is that at the end of August I am taking the RV6 to S France for two weeks, where currently it is +30c !! There are no cowl flaps and the inlet at the front is quite small compared to a Piper or Cessna.
Last month near Bordeaux (33deg) the 360 in our Piper Arrow was nudging the red in the climb to FL70.
Felt it prudent to level off for a while to see oil temp drop.
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John
Cooling issues in the south of europe are normal, I guess that your RV just like my DR400 gets its speed from being very efficient aerodynamically, some of this is due to not having too much cooling drag.
The result of this is that the cooling is enough for the cruise but at climb speed and Power there is not enough cooling, this is managed by step climbing the aircraft, the DR400 at MTOW with a ground OAT of +30C can expect to climb to 4000ft before the oil temperature climbs to the upper end of the Green part of the gauge and 5000 ft will probably just short of the red line.
Simply stopping the climb and setting up the 60% power cruise will bring the oil temp back to the normal range within a few min.
In the UK where we are usualy hard pressed to get above 5000 ft due to Class A airspace and dont have too much high ground to deal with oil temp is not a perfomance issue but at places like Granada that can hit +40C in the summer and is surounded by high ground oli temp issues can govern your ability in climb clear of terrain.
An early start is sometimes required in central Spain before the heat of the day kills the climb performance. Also you should choose the altitude you wish to stop the (step) climb at, most long range flying is done VFR on airways and being forced to stop at the IFR level going in the wrong direction wont make you any friends with ATC so plan your climb so that you can get to the next VFR level before the oil temp gets out of limits ( if you dont quite get to the next VFR level at least you will be at the IFR level going the right way!).
The result of this is that the cooling is enough for the cruise but at climb speed and Power there is not enough cooling, this is managed by step climbing the aircraft, the DR400 at MTOW with a ground OAT of +30C can expect to climb to 4000ft before the oil temperature climbs to the upper end of the Green part of the gauge and 5000 ft will probably just short of the red line.
Simply stopping the climb and setting up the 60% power cruise will bring the oil temp back to the normal range within a few min.
In the UK where we are usualy hard pressed to get above 5000 ft due to Class A airspace and dont have too much high ground to deal with oil temp is not a perfomance issue but at places like Granada that can hit +40C in the summer and is surounded by high ground oli temp issues can govern your ability in climb clear of terrain.
An early start is sometimes required in central Spain before the heat of the day kills the climb performance. Also you should choose the altitude you wish to stop the (step) climb at, most long range flying is done VFR on airways and being forced to stop at the IFR level going in the wrong direction wont make you any friends with ATC so plan your climb so that you can get to the next VFR level before the oil temp gets out of limits ( if you dont quite get to the next VFR level at least you will be at the IFR level going the right way!).
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A and C
In late August I am hoping to fly down from Biggin Hill to S.France at 4,000ft or more depending on clouds as I will be VRF, but would certainly like to get up into the cooler air, where it is less bumpy ( one of the problems with the RV6 is that although it has high wing loading, it is very rigid airframe and in turbulence it does not ride it well, unlike the Robin DR400/180 I used to take to France and Italy ). I have found that if the OAT is below 16c or there abouts then the temp of the CHT and OIL are fine. So yes, I will be doing the step climbs if needed. Thanks John
In late August I am hoping to fly down from Biggin Hill to S.France at 4,000ft or more depending on clouds as I will be VRF, but would certainly like to get up into the cooler air, where it is less bumpy ( one of the problems with the RV6 is that although it has high wing loading, it is very rigid airframe and in turbulence it does not ride it well, unlike the Robin DR400/180 I used to take to France and Italy ). I have found that if the OAT is below 16c or there abouts then the temp of the CHT and OIL are fine. So yes, I will be doing the step climbs if needed. Thanks John
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Step climb versus climbing at a higher indicated airspeed.
I read some "good" comments about step Climbing to cool the cylinders and the oil.
Why not simply climb at a higher IAS and prevent the problem completely while gaining better forward visibility doing so.
And? It prevents the cold-hot-cold-hot-cold cycle completely.
In warm weather, where oil and cyl head temps might be an issue, just climb at a higher IAS and keep the temps stable.
Why not simply climb at a higher IAS and prevent the problem completely while gaining better forward visibility doing so.
And? It prevents the cold-hot-cold-hot-cold cycle completely.
In warm weather, where oil and cyl head temps might be an issue, just climb at a higher IAS and keep the temps stable.
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Vilters
As you say climbing at higher IAS can help but it reduces the rate of climb and increases the time the engine spends at full power and so producing the most heat.
I can see this tactic being of use in aircraft that have cowl flaps where you can adjust the amount of cooling air but it is likely to increase the time it takes an aircraft with a fixed cooling system to get to cruise altitude.
What is clear it that no one tactic works for all aircraft so it's best to get to know the best tactic for the aircraft you are flying.
I can see this tactic being of use in aircraft that have cowl flaps where you can adjust the amount of cooling air but it is likely to increase the time it takes an aircraft with a fixed cooling system to get to cruise altitude.
What is clear it that no one tactic works for all aircraft so it's best to get to know the best tactic for the aircraft you are flying.
