Remote oil thermostat

[jrthomas]

Are most of you running the oil thermostat? I can't seem to find any information on purging the system with the thermostat. It seems to me that the thermostat redirects the flow through the oil cooler when the temp reaches a certain level and by purging a cold engine, the oil cooler is being bypassed. I had a small leak on one of my oil cooler fittings and may have allowed some air in. I need to purge but I want to make sure I do it right. Thanks, James Thomas

[Paul Z]

All of the new SLSA use oil thermostats, mine didn't come with one, but John has said I could add one when I do the 5 year hose replacement. I'd need to go read the instructions to better understand how they work. They mount them behind the engine on the lower engine mount tubes. I do have some photos of the installation if interested, and I also have the installation instructions. I could make a PDF of the installation instructions as well.

[jiott]

Kitfox sells an oil thermostat kit with all the hoses and fittings you need, as well as instructions.

I purged my oil system just the way Rotax says to do it and had no trouble because of the oil thermostat. I believe the thermostat never totally blocks off the oil cooler, so when you purge you will move some oil thru the cooler.

[Dorsal]

My experience is the same a Jim's, I have a thermostat and use the normal purge procedure.

[jrthomas]

I suspected, based on the lack of any info otherwise, that the purging process would be the same. The oil thermostat I have is the same one that Spruce sells, (#15-05849). Their info says it remains 10% open so, hopefully, purging will displace any air that I might have let into the oil cooler. Thanks again, James Thomas

[Slyfox]

crank the engine with the mags off. if you have oil pressure you are purged. you can also do the prop turning until it gurgles in the tank. the oil thermostat works by bypassing the cooler, same thing as going through the cooler. when it gets hot it allows passage through the cooler. not an issue for purging air at all. the air doesn't know the thermostat is there.

[jiott]

I'll have to disagree with every point you make:

You do not have a successful purge until you have oil pressure AND solid valve lifters.
A gurgle in the tank only means you have pushed all the oil out of the crankcase; it does not mean you have purged all the air out of the oil system.
Air trapped in the oil cooler must get purged out or when the thermostat opens you will get a slug of air into the system-not good. Fortunately the 10% going thru the cooler even with a closed thermostat will purge the air out of the cooler if you give it enough time. Therefore it is somewhat of an issue in purging.

[Paul Z]

You need to purge the system with pressure. There is a pressure line to put on the oil return side of the oil tank to push oil from the tank to and through the engine to purge the air from the engine, oil cooler, oil thermostate, and the oil lines. You need to get all of the air out. At the Rotax Maintenance Training class, the taught us that anytime you change lines, or remove the oil tank. The system needs pressurized to push oil through the system, and purge the air from the system.

[TahoeTim]

Do we have two conversations going on here?

It seems like some of you are discussing purging after installing the kit and some of you are talking about pre-flight burping of the crankcase.

[Slyfox]

I stand behind what I said. the question was opening a line and have some air. If you are starting a new engine, that requires much more. you have air in your cooler it goes out real fast when the thermostat opens. I never worried about that. I have my new engine at 500hrs and the old one went about 2200hrs. never an issue and yes I have the lockwood thermostat, have had it forever on both engines. I also believe the air in the cooler goes right into the tank not the engine on flow. correct me if I'm wrong. still I've never had an issue with this. If there is air in the system, the oil pressure will be none. this is for sure.

[Slyfox]

I'll have to disagree with every point you make:

You do not have a successful purge until you have oil pressure AND solid valve lifters.
A gurgle in the tank only means you have pushed all the oil out of the crankcase; it does not mean you have purged all the air out of the oil system.
Air trapped in the oil cooler must get purged out or when the thermostat opens you will get a slug of air into the system-not good. Fortunately the 10% going thru the cooler even with a closed thermostat will purge the air out of the cooler if you give it enough time. Therefore it is somewhat of an issue in purging.


first point. this is not true when just opening a line. the lifters are already solid as you call it. if air is in the line and you crank it, pressure will be none. if you just crank it with the mags off, after a few cranks it should come up on the pressure, if not, let it cool on the starter and try again. once it comes up your done.

point two. If you cracked a line you can turn over the engine with mags off and purge the system. yes this will get the air out. but you need to crank the engine to make sure the oil pressure is up. if not, well you can wear your arms out or crank the engine mags off until the pressure comes up.
Now, you can yes aid this by adding air pressure into the vent while cranking to get your pressure. I've had to do this. not a bad idea. again main thing is oil pressure. like 60psi cold and can go down to 40 when warm.

point three. if you are worried about it. when your engine is new or the system is new, yes you can put some oil in the hoses and cooler. but for cracking a line, the cooler still has oil in it, should not be a problem. I change my oil, no lines come off. the amount of oil is real small. so I don't do it. I remove the old filter and fill the new one. I don't worry about air in the system. the little bit I get is pushed out by just turning the engine over with mags off. generally takes about 3 to 4 seconds of cranking to get THE OIL PRESSURE.

[Slyfox]

one more thing to say here. Is your cooler hooked up right. I have to look at an oil diagram. but I think you can hook it up wrong. the tank should be hooked up direct to the pump on the engine and than out to the cooler and than back to the tank. like I said I need to look at the oil diagram. I'll try to look it up if I get a chance.

[Slyfox]

ok. I just looked at the rotax manual and it show the cooler is in line between the tank and the input of the pump. I think this is a mistake. why? I'm a transmission man. I have a shop and have been building transmission for 35+ years. with that said, all transmission pump fluid into the pump from the filter and than it goes out to the cooler. gets cooled and than goes back into the sump. general transmission operation. I think that is true with an engine on a vehicle as well. so with that said. I'm going to look at my kitfox and see how I set up the cooler thermostat and cooler. been way to long. makes more sense to put that cooler after the pump. if there is air it just goes back into the tank. not going into the pump and damaging things. theory anyway. works on automotive.

[jrevens]

I believe that with a Lycoming, for instance, oil is re-routed from the pump to the oil cooler by a Vernatherm that closes off a port in the accessory housing (on older engines that's done by a spring & ball "valve"), then it flows back to circulate through the engine until finally ending up back in the sump to be picked up by the pump again. A Vernatherm is a thermostatically controlled valve, while the spring & ball relies on the viscosity of the oil to do what it has to. I'm not saying that your idea is wrong, Slyfox. I'm just unsure if there is a good reason that it's done the way it is by Rotax. With engines like Lycomings, oil returns to the sump from many different places. With a dry sump engine like the Rotax it's a different matter of course, so the cooler could be installed upstream of the tank. But there may be some advantage in doing it the way they do because the oil will probably be cooler coming out of the oil cooler & going directly to the engine rather than coming from the oil tank where it mixes with oil that has been sitting in the tank (in the warm or hot engine compartment). Additionally, the oil may actually be pre-cooled a little by sitting in the tank before going to the cooler, and that will result in cooler oil ultimately reaching the engine.

[Slyfox]

understand. but many applications on the early engine didn't even have a cooler. than a cooler is put in. rotax shows before the pump. I don't think this is wise is all. all my applications I ever worked with has oil inlet straight from the sump via filter. than put through the cooler, than back to the sump. actually there is the internal lube of the transmission than sump. that gives the coolest oil for lubrication of planetary gears. smart system. on rotax it's sump, cooler, than pump. I just don't think it is wise considering the air that could be in the cooler at least on first start up and if people removed the lines for oil change(which I don't). I personally don't think it matters on the position of the cooler being after the engine. meaning the hose on the bottom of the engine to the cooler and than back to the tank. that is essentially the sump for this engine, don't you agree. I still don't know how mine is set up.

also I think if the oil is cooled and than put in the sump which is cooled from air coming in the engine area than it will be cooler.

[jiott]

I understood that the original question for this thread was for purging a new installation.

Also i don't understand why anyone would consider deviating from the Rotax startup/installation instructions on a brand new $20,000 engine just to save a little time or whatever. Those instructions have proven good on multple thousands of engines over many years. It is fun to speculate on why they do some things the way they do and maybe there are improvements to be made, but when the dust settles I for one am going to follow their procedures.

[jrevens]

... that is essentially the sump for this engine, don't you agree. ...
also I think if the oil is cooled and than put in the sump which is cooled from air coming in the engine area than it will be cooler.
Yes, of course... the tank is a remote "sump".
My point was that the oil will, or should be coolest when it is coming out of the cooler. The oil in the tank will tend to be cooled down from when it leaves the engine, but is probably still warmer than the oil leaving the cooler- it is in an area surrounded by warmer air. The chances are that the colder the oil is before it enters the cooler, the colder it will be exiting the cooler AND the more efficiently the cooler will operate because of a smaller temperature differential.

[Slyfox]

but the discussion I thought was on air in the system and air in the cooler when first fired up with a new system. I do believe also that there is about 10% flow through the cooler at all times. now for the na sayers on bleeding the system and using pressure as your guide. How do YOU know when the air is out?

[jiott]

Refering to the Rotax 912 Service Instruction SI-912-018, after you hook up the purging circuit and apply air pressure, you rotate the propeller BY HAND (says do Not use the starter) 20-60 times until you see oil pressure registered on the gauge. Of course while you are doing this you can visually observe the return oil flowing into the catch bottle you have installed. It will flow out along with blurps of air until it becomes a solid stream. You then reconnect everything normally and run the engine until warm for a few minutes. Then you shut down and check each valve lifter for a solid feel which only then insures you have properly purged out all air. Apparently the lifter area is the last and hardest place to purge, therefore it is the final thing to check. Sorry to repeat what is readily available to everyone, but not everyone bothers to read these things.

[Slyfox]

whatever I guess I'm not going to get anywhere here. again you are talking a new motor install. this discussion is on a line that was leaking and if there was air in the system from it if I read it right. again I will say crank the engine over with mags off. if the pressure is up you are ok. tighten the line and go fly.

[jrevens]

I appreciate the conversation here... available or not, it's good information and I need all of it that I can get. I didn't start this thread, but thank you all anyway.

[DesertFox4]

FYI guys, you can all vote or rate a thread at anytime for all those folks searching our archives in the future. If you like a thread please rate it and stars will be attached for future reference. Thanks to everyone for another good info filled thread.

[Kurt.A]

I too have been following this thread with curiosity. The fact that the eng oil cooler is plumbed into the suction side of the eng oil pump disturbs me. Automotive eng oil coolers are rarely used in the gasoline world however they are extensively used in the heavy duty or diesel engs. I have been a Tech for the largest Caterpillar dealer in the world for the last 28 years. Every single Caterpillar eng ever produced has the oil cooler on the pressure side of the eng oil pump and is also downstream of the eng oil filter. To me it is logical to cool the oil after the pump and filter for the following reasons:
1) Pressurizing oil with a pump produces heat.
2) Filtering cooled oil has the potential to open the filter bypass valve more often and for longer periods of time allowing unfiltered oil to enter into the lubrication system.
3) Having the cooler in the suction circuit leaves the system open to extra possible leak points on the suction circuit. This would allow the potential for a constant stream of air to be entering into the lubrication system. Yes air will enter the suction circuit long before a visible external oil leak will be observed.

With regards to having air in an eng's lubrication circuit as per the original post. I have seen many times the devastating results inside an eng to it's components from air bubble implosions. An implosion is the result of an air bubble collapsing at high pressure allowing the surrounding liquid to impact the metal with incredible force. This can be readily seen on eng bearings, crankshafts, the coolant side of cyl walls, eng oil pumps and the list goes on. I have never seen this damage to a valve train component including lifters however for the most part Caterpillar engs use solid lifters. IMO the air that has managed to enter the system gets purged from the oil prior to entering the valve train components as this is near the end of the lubrication circuit. The comment in a previous post made about ensuring the hyd lifters be completely filled with oil is also very critical to valve train stability. Hyd lifters should always be manually pumped full before installation to the eng.
Unless someone wishes to convince me otherwise I will definitely be changing the way my Rotax eng oil cooler is plumbed. Because Rotax says so does not count here. My sincerest gratitude to the board members that have brought this fact to everyone's attention.

[Av8r3400]

Rotax engines do not have a scavenge pump removing the oil from the engine back to the sump. They rely on crank case pressure to do this. I would not put any components on that side of the oil system that may impede the flow. This is just begging to hydrolock your running engine making for instant total destruction.

There is no provision that I can see to put the cooler after the pump yet before the engine without modifying the engine case and or pump itself. Additionally I would not do this because it would introduce all of the lines and the cooler itself to holding full engine oil pressure. A failure of any of these multiple connections, lines and passages will result in a pressure oil leak, which can quickly pump all of your engine oil overboard which will totally destroy the engine very quickly.

There is a lot of overthinking a non problem here. The engineers at Rotax understand their engines and know how to keep them working, reliably. This is the experimental world, so you can do as you wish, but I'll follow the installation and operating manuals.

[Slyfox]

I personally don't see an issue with putting the cooler after the pump. It's done on many applications in automotive. the cooler that is put on is free flow for one. I am disturbed more that the cooler is put on before. first off how do you insure that all air is out of the cooler, you really can't and for first start up that little pump can have problems with air going through or into the bearings of the engine. I know when I first started my engine I had filled all lines with oil first. I took my line from the tank and filled there and removed the line off the pump inlet and had that spot as the leak out. meaning when I had oil coming out of that line my cooler and such was full than I put the line on the pump inlet. this proved very good and it took very little to purge the system and fill the lifters. which I did have the covers off the valves and checked like I was suppose to before firing up the engine.

again this discussion was on if air or a leak was found on one of the lines. in that case you seal the system and crank over with mags off and look for pressure. that simple. if no pressure you need to make sure and recheck the purge and adding air to the vent is one of them. of course the top of the tank is on as well as the cap. I sit in the airplane with the vent in hand and shop air blown little at a time and crank over the engine until the pressure come up. yes it works real well. take care have a nice day:)

[Slyfox]

Rotax engines do not have a scavenge pump removing the oil from the engine back to the sump. They rely on crank case pressure to do this. I would not put any components on that side of the oil system that may impede the flow. This is just begging to hydrolock your running engine making for instant total destruction.

There is no provision that I can see to put the cooler after the pump yet before the engine without modifying the engine case and or pump itself. Additionally I would not do this because it would introduce all of the lines and the cooler itself to holding full engine oil pressure. A failure of any of these multiple connections, lines and passages will result in a pressure oil leak, which can quickly pump all of your engine oil overboard which will totally destroy the engine very quickly.

There is a lot of overthinking a non problem here. The engineers at Rotax understand their engines and know how to keep them working, reliably. This is the experimental world, so you can do as you wish, but I'll follow the installation and operating manuals.

no insult here, but are you an engineer. I've been working on hydraulic systems for years. coolers generally plug up from debris in the cooler created by a failure. also if you are saying there is a chance the cooler being plugged and close off flow. think about this. if the cooler is restricting it can cause problems on the suction side. what I have seen is things will work normally than the vacuum gets to great and than the pump quits without warning. seems to me you can taxi out and take off and than the oil pressure goes to nothing in this case. seen it many times on transmissions. so I guess it can go both ways.

not sure what the answer is here. I know my system is working fantastic, so I probably won't change it. but to those starting a new engine, they must insure that cooler is free from air from the start up.

Now this is another thing I do. when I first get to my airplane I burp the engine. I push the airplane out of the hangar and than I get in. turn on the master keep the mags off and pull the choke. than I turn over the engine for 3 seconds. this does two things, it puts fuel in the cylinders, two it makes me aware that the oil pressure is there, if not, it gets more crank time without choke to make sure pressure is there. do any of you insure oil pressure before start. you should. that's all folks, have a nice day.:)

[Slyfox]

Kurt, you wrote:
3) Having the cooler in the suction circuit leaves the system open to extra possible leak points on the suction circuit. This would allow the potential for a constant stream of air to be entering into the lubrication system. Yes air will enter the suction circuit long before a visible external oil leak will be observed.

This is very very true. I have thought of this also on this discussion. this in itself will probably make me change mine over when I change all the oil circuit rubber this next annual. it is much safer to have as little chance of leaks on the suction side of any pump. in our situation having the cooler and the thermostat is a big worry for this. thanks for mentioning.

[Av8r3400]

Yes, actually, I am an engineer. I work in a different area now, but my background is mechanical engineering.

This isn't a heavy diesel or automotive application where when you blow a pressure oil line you can stop, shut down the machine and fix it. It's an airplane. When you blow an oil line you will quickly loose the engine. This means you land. Hopefully safely, without injury or loss of life.

As an experimental, you can do as you please and I wish you luck. I choose to follow the Rotax engineers' advise as to cooler location and operations. They know more than I do.

[Slyfox]

I just looked at my plane and yes it is put together just like rotax says. will I change it. don't know. I run on the premise of, "if it ain't broke don't fix it." I know when I put my lines on I used silicon on the hose to fittings and then the clamp. I've been doing this forever on auto applications. if the clamp happens to loosen a bit it is still sealed. now I don't use cheap silicon I get mine from ford. it really dries solid. Now another thing I did is put that thermostat on the top of the gear box. my theory is it has the line coming out of the tank going up high. makes the oil stay in the tank. I checked my oil level today and it's been since sunday that I last flew it. the oil was all the way up. I also have it plugged in, yup I do that also, I know that is another thread going. but I plug my plane in and forget it. it has the reise system with the thermistor to control temp and a ring around the tank and the element on the engine. engine was warm and the oil at the top of the stick. it's always like that. even after sitting for about a month here recently cus it was real cold and windy, flew the rv instead. the oil was still showing on the stick when I checked it. I think having my thermostat on the gear box does this.

will I change my line routing, more than likely not. but I do now understand any leak in the lines before the pump can be BAD.

[jiott]

A leak on the suction side can be bad alright, but I agree with Av8r3400 that a leak on the pressure side is much worse. I also think that a cooler on the pressure side is more likely to fail because it is seeing relatively high pressure (way higher than a coolant radiator) cycles all its life. Most oil cooler failures I have seen are from pressure fatigue rather than contaminant blockage.

[jiott]

One thing I have learned after 40 years as a hydraulics engineer is that there is always more than one way to do something, as we see here in this thread, so choosing the best way is usually a compromise between many factors such as:

Proper function
Longevity
Ease of installation
Ease of maintenance
Failure modes & probability
Results of failures
Likelihood of errors in installation & maintenance
First cost & life cycle costs
Overall reliability
Environmental factors
Cosmetic appearance
I have probably missed several areas, but you get the idea. The engineer has to weigh all these things, and I tend to trust the factory engineers who focus their whole effort and have many years of product experience to call upon. That is compared to those of us on this forum having fun trying to second guess them in a few minutes of our spare time. Hey I know this is experimental aircraft and there have been many new and better ideas come out of it, but be carefull, you are dealing with your life and a $20,000 engine. My 2 cents.

[Slyfox]

but in my line of work, these type of coolers have not been a problem. now the ones in the radiator, oh my. but those generally will fail with pressures over let say 80psi. and have seen it. aka the Nissan radiator failures which is a direct result of cooler line pressure up tward the 120psi area. which can be controlled with a different spring. the stacked cooler like we use can even withstand that pressure. but those radiators not a chance. not trying to muddle anything just saying. mine will probably stay the same for it is WORKING the way it is and I like the fact that my system keeps the tank level up. but knowing that there is like 8 connections between the tank and my oil pump inlet has got me to say the least, interested in keeping things sound.

[Kurt.A]

Did not mean to get under anybody's skin with my previous post. Yes we are all allowed our own opinion, we have many to thank for our freedom of speech. I fully understand the potential for an external leak being disastrous but no more disastrous than any other eng failure which could easily be caused by a variety of reasons. The plate coolers are very tough units as compared to the coolant radiators. They live right in prop wash and can be subjected to stones and pebbles even on a paved strip. something as simple as a pebble strike could cause a cooler to leak. With the cooler on the pressure side the leak would be obvious and draw immediate attention. With a leak on the suction side through the same pebble strike would still cause the eng to go down after many hours of aerating the eng oil and creating huge dollars in repairs. With the environment that I will be flying in I can definitely see that eng life would be increased with plumbing the cooler in after the filter. Just honestly makes more sense to my brain.

[jiott]

Kurt, just curious if you plan to plumb your cooler after the filter there is nowhere on the 912 to put it except in the scavenge line from the bottom of the crankcase to the oil tank. Or are you planning some modification to the engine case to get an oil in & out port on the pressure side?

[jrevens]

Kurt, just curious if you plan to plumb your cooler after the filter there is nowhere on the 912 to put it except in the scavenge line from the bottom of the crankcase to the oil tank. Or are you planning some modification to the engine case to get an oil in & out port on the pressure side?

I had the same question in mind with one of my previous posts. There's a lot to consider here, and I tend to agree with Jim and some others who like the cooler where Rotax says to put it. I'll say again that I believe the engine will see higher oil temps if the cooler is piped between the engine & the oil tank. Is it enough to be a factor worth thinking about? I don't know. But how do you propose to install the cooler "downstream of the oil pump & filter"? The only access I know of is downstream of the whole engine. The only pressure on that line is crankcase pressure. It seems to me there might be more chance of potential clogging of the cooler on that line than after that big "engine moisture, sludge & any other crap that may come out of the crankcase" trap called the oil tank.

[Kurt.A]

Tapping into the oil supply is relatively simple. I agree that plumbing the cooler into the return to tank line would not be wise. What I would propose is to spin off the oil filter. Fabricate or purchase an adapter plate that installs in place of the filter with an inlet and outlet port. These are readily available for automotive use but would require some research to find one that fits the filter mounting dimensions. From the adapter plate you would run steel braided hose to a remote mount filter housing then to the cooler and then back to the filter adapter. You could also do this using thin wall 4130 tubing which would probably be the safer route. A word of caution to those reading in, steel braided hose will harden after about 3000 hrs and become a serious safety concern. A cooler bypass valve would be wise as well with a pressure differential setting of about 20 PSI for cold starts. I am not saying that Rotax engineering is wrong, but I am saying that in cold climates where I live and intend to fly a cooler on the suction circuit scares the bejesses out of me far more than the potential for an external leak or even a total rupture.

[Av8r3400]

One last point I'm going to make here.

I have a 912 UL (80 hp) in my yellow plane. I have NO oil cooler on it. Zip, zero, nada. On the hottest of summer days, after long sustained full power climb, my oil temp may get to 250 degrees Fahrenheit. Yes I live in Wisconsin, not Arizona or Nevada. But it does get into the high humidity, 90s here during the summer.

I use Mobil 1, Racing 4T oil. With this oil my temp redline from Rotax is 280 degrees Fahrenheit. I've been told by LEAF, that this oil remains stable and will not coke well above 320. I don't need an oil cooler. I don't want the complexity of tubing and weight of an oil cooler on this already nose heavy plane.

With modern oil technology, high temps usually aren't the problem. I've seen more problems with prolonged low oil temps.

Just something to think about.

[Slyfox]

does anybody have the info on the oil circuit for the 912 internally. just curious on the thoughts here on the crankcase pressure for the return line. I don't see how crankcase pressure alone can burb the engine for normal use. I believe it's also mixed with oil pressure from the pump. just trying to do a mental on this. the reason I say this, there is a big line coming off the bottom of the engine. I would be interested in a flow of this line. I have a device called a sonna flow that I can put on this line to do just that, it checks flow. I don't have any time now to install this on mine at time being but would be interesting to see what it is. think of this. if the engine needs so much oil from the tank to operate, the return has to be as much to keep the level up. see my meaning. the flow back to the tank is the same as what is leaving. with that in mind why wouldn't it work on the return line the cooler that is, just saying.

[jiott]

The reason it wouldn't be wise is that the scavenge line coming off the bottom always has oil in it (the same amount being pumped out of the tank) but it also has some air (combustion blowby) in it. I doubt an oil cooler in this line would work very efficiently with a mixture of oil and "air" in it. The oil tank is designed, with its screen etc. to separate out the air before it gets pumped back into the circuit. If you don't think there is air in this line, think again. The only thing pushing oil out of the crankcase back to the tank is crankcase pressure; there is no oil pump pressure down there because the crankcase is common with the oil tank which is vented to atmosphere. I know engineers are clever fellows but there is no way they can design the crankcase blowby pressure to push EXACTLY the right amount of oil back to the tank without any air in it. If the flow rate was even a teensy bit too slow the crankcase would eventually fill up with oil and hydrolock the engine. The only choice is to always blow more than enough oil back to the tank, keeping the sump "dry", which means that there is always some air in this line. By the way the Rotax maintenance manuals which show the oil circuit details are available free to all on the rotaxowner.com website.

[Slyfox]

thanks for explaining, makes more sense now. must be why I get a little oil out the vent line. I'm sure if I make my vent longer and loop it higher than the tank might help. another project to do. that's what makes an experimental so fun, lots of little things you can do to it. have a nice day. oh also, will have to download the engine manual one of these times. hope you all have a nice Christmas. :)

[Kurt.A]

One last point I'm going to make here.

I have a 912 UL (80 hp) in my yellow plane. I have NO oil cooler on it. Zip, zero, nada. On the hottest of summer days, after long sustained full power climb, my oil temp may get to 250 degrees Fahrenheit. Yes I live in Wisconsin, not Arizona or Nevada. But it does get into the high humidity, 90s here during the summer.

I use Mobil 1, Racing 4T oil. With this oil my temp redline from Rotax is 280 degrees Fahrenheit. I've been told by LEAF, that this oil remains stable and will not coke well above 320. I don't need an oil cooler. I don't want the complexity of tubing and weight of an oil cooler on this already nose heavy plane.

With modern oil technology, high temps usually aren't the problem. I've seen more problems with prolonged low oil temps.

Just something to think about.

Now that is an excellent point! I was not aware that I could effectively remove the cooler from the circuit without causing oil degradation. I agree 100 percent that oil temps of your experienced 250F are perfectly fine with the use of high quality synthetic oils. Plus you get the advantage of less forward weight, less complexity, and less failure points. Every ounce of weight saved is a benefit in my opinion. Thanks for posting and I am glad we had this discussion.

[AirFox]

Can someone give me an example of "prolonged low oil temps"?

[Av8r3400]

Prolonged operation with the oil temp never exceeding 150 degrees Fahrenheit.

This causes a buildup of dissolved water in the oil, hampering the lubricity and potentially causing corrosion internal to the engine and gearbox. This is especially important if you are running 100LL.

When running 100 LL it is imparative that oil and cylinder head temps exceed 200 degrees to keep lead buildup from happening.

[AirFox]

Prolonged operation with the oil temp never exceeding 150 degrees Fahrenheit.

This causes a buildup of dissolved water in the oil, hampering the lubricity and potentially causing corrosion internal to the engine and gearbox. This is especially important if you are running 100LL.

When running 100 LL it is imparative that oil and cylinder head temps exceed 200 degrees to keep lead buildup from happening.

Thanks for the advice. I have a uls with the newer cylinders. I have the oil cooler and thermostat. My oil temp never gets over 200. Usually runs around 160. The last month I covered the oil cooler and still didn't get the temps over 200. Good real world info in this thread.

[Av8r3400]

I don't have one, so someone please correct me if I'm wrong, but I thought that the oil thermostats under discussion in this thread are designed to open at around 180º F.

This would also jibe with what we were told in 912 training that the water doesn't really start evaporating off from the oil until that 180º level has been reached.

[jiott]

I have the oil cooler mounted on front of the coolant radiator and have the thermostat (I believe it is 180 degree but not 100% sure). When the weather turned cold last month I was not seeing oil temp much over 160. Then I taped over the oil cooler with a 2" wide strip of aluminum tape (which also blocks air flow thru that part of the coolant radiator) and now see my oil temps up at 210-220.

Also remember that the oil temp sensor is at the oil pump, which is probably the coolest point in the oil circuit. I wouldn't be surprised if the oil temp in the engine galleries was over 250 degrees.

[Kurt.A]

Can someone give me an example of "prolonged low oil temps"?

Prolonged low temperature oil does not allow water to evaporate off as posted. The scary part of all this is the chemical reaction that takes place in the oil. In severe conditions the oil turns turns acidic and starts to eat away at the metallic components within the eng. This is one of the reasons to use a very high grade synthetic oil. The modern synthetics contain considerably more additives that combat these types of issues. Best defense is to maintain normal operating temperatures, use high quality synthetic oils and perform your oil changes religiously.

[Meyertheflyer]

I have an oil thermostat that I'd like to install. Does anyone have a picture of their installation on a model 7 super sport that they could share. If not, I'll post one when I'm finished. Thanks

[Paul Z]

I just installed mine. I looked at a new SLSA at the Factory, it was a lot easier than I thought. I'm going to the airport to finish my annual. I'll take some photos, since my cowling is off I can get them pretty easily.

[Meyertheflyer]

Thanks Paul, I appreciated it.

[jiott]

Here are some photos.

[Meyertheflyer]

Those are very helpful. Thanks Jim

[cubtractor]

I had read some information on oil temperatures some years ago but it was along the lines of the link listed below.

http://www.reiffpreheat.com/Article-Visser3.htm

[Paul Z]

From the bottom

[Paul Z]

From the co pilots side, towards the firewall

[Meyertheflyer]

Thanks, I'll use these photos to help install. I was flying my Kitfox at 14000 feet and the oil temp was only at 138 degrees. This should solve that issue.

[mr bill]

I vibration isolated mine on top of the engine. The instructions were very clear not to hard mount the oil thermostat.

[HighWing]

I haven't been following this thread for reasons that will be forthcoming, but being away from projects and with time on my hands as I visit 3000 miles from home, I started reading and thought I might share some thoughts. I guess it was likely in 1994 or 5 that I went to the factory fl-in to see what folks were doing and take some pictures to help me on my new project. One of the things that struck me was the number of guys with the factory oil cooler had most of the face blocked off with tape. And this was in August where bitter cold was not a factor in too cool oil. The first thing I decided to do was use the smaller oil cooler available from Earls. The factory cooler was the wide one - about 8 inches wide between inlet and outlet ports. The narrow one was about 5 inches. I also started working on shutters that could be controlled from the cockpit. That setup is what I started flying with from day one.

As was mentioned, the need of an oil cooler is marginal in most US climates. I generally flew with the shutters closed. I would occasionally open them on long climbs as necessary. I was aware when the thermostats became available but in the beginning they seemed a bit cumbersome and the multiple lines discouraged me and most of those I flew with that I trusted for advice. To this day, I like the simplicity of the small cooler and the shutters. I was reluctant to discuss the shutters as at the time we had a business and were not advertisers on this forum and in the spirit of fair play we tried to adhere to the forum rules regarding promoting stuff not found on the left edges of forum pages. We have shut down our business so free to talk, I guess.

Some comments on before or after the oil pump. I suspect the factory recommendation of the cooler before the pump is simply that is where it fits given the design of the engine. Whether the designers even considered the possible need of an oil cooler - who knows for sure, but it is what it is. With that in mind, I strongly believe that with the several email lists in the old days and this forum, alongside the very active service letter efforts both from all versions of the Kitfox kit manufacturers and Rotax, if there was an issue with sucking air from the inlet mounted oil cooler we would have heard of it at least once. Someone mentioned over thinking this issue. I am pretty much convinced this is the case. When our group of six to eight were flying together 40 to 50 hours a year, we saw a lot, talked a lot and interacted a lot with other Kitfox guys and nothing on this ever came up. The one and only issue we ever had on one of our back country sojourns was an ignition module failure and that was repaired in the field with a butane soldering iron someone brought along, but that is another story. I'm sometimes a bit concerned about all the bells and whistles literally. We automate and then rely on flashing lights and chirpy alarms to get our heads up rather than doing the old fashioned instrument scans. A recent accident report in Sport Pilot tends to bear this out

[AVDOC]

Thought I would add some pictures of the oil thermostat that I installed on my Model 4 Speedster. It is the newer thermostat that Rotax appears to bless. I purchased it from spruce

It was a little easier to plumb, and is a little smaller than the other stats.

Also have the oil shutter's installed just in case it's needed

[jrevens]

A question for the group - I have one of the common silver-colored aluminum oil thermostatic valves, as shown in a lot of pictures in this thread. I'm getting ready for my first engine run, preceded by the oil-purge procedure specified by Rotax of course. It seems as though with that valve in the circuit the oil cooler will probably not be filled with oil during the purge. Is this a worry that I should be thinking about, and has anyone attempted to fill the cooler with oil before that first start?

[Paul Z]

They have a hose that hooks up to the return line side of the tank. You put the return line hose in a bucket, hook the hose up to a compressor, pinch off the overflow vent hose, and turn the prop like your trying to burp the system. Once you start seeing oil pumped into the bucket your done. Remove the hose, replace the return oil line to the oil tank, and your system is purged. I have a hose sitting on the shelf I could loan you.

[jiott]

John, I didn't prefill the oil cooler (I don't think most people do) although that certainly wouldn't hurt. As has been said before on this forum, the oil thermostat never completely blocks the oil path thru the cooler. So as you purge the system per instructions a small amount of oil is passing thru the cooler and will fill it up. To make sure, I prolonged my purge for a longer time than called for. After the purge was done and I fired it up, oil pressure came up immediately. I watched to see if it would drop off, indicating a big air bubble going thru, but it stayed steady the whole time. I did have to do a couple of extra runs before one of the lifters felt solid; didn't re-purge, just ran the engine for a while and then checked the lifter again.

[jrevens]

They have a hose that hooks up to the return line side of the tank. You put the return line hose in a bucket, hook the hose up to a compressor, pinch off the overflow vent hose, and turn the prop like your trying to burp the system. Once you start seeing oil pumped into the bucket your done. Remove the hose, replace the return oil line to the oil tank, and your system is purged. I have a hose sitting on the shelf I could loan you.

Thanks Paul... I understand all that, and I do also have a hose & pressure regulator/gauge assembly to do the purge. My concern is that during that purging operation the thermostatic valve will be bypassing the oil flow so that it isn't going into and through the cooler coil. This seems like it could be a problem, when the oil warms up and the valve re-directs oil through the cooler. It seems like there would be a big bunch of air pushed out of the cooler and going right to the oil pump inlet. If this has been a non-issue for others I'll be happy.

[jrevens]

John, I didn't prefill the oil cooler (I don't think most people do) although that certainly wouldn't hurt. As has been said before on this forum, the oil thermostat never completely blocks the oil path thru the cooler. So as you purge the system per instructions a small amount of oil is passing thru the cooler and will fill it up. To make sure, I prolonged my purge for a longer time than called for. After the purge was done and I fired it up, oil pressure came up immediately. I watched to see if it would drop off, indicating a big air bubble going thru, but it stayed steady the whole time. I did have to do a couple of extra runs before one of the lifters felt solid; didn't re-purge, just ran the engine for a while and then checked the lifter again.

I didn't see this, Jim, before I posted the last reply... thank you. That's what I was hoping to hear.