Remote oil thermostat

[Slyfox]

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

1. You do not have a successful purge until you have oil pressure AND solid valve lifters.
2. 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.
3. 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.