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Purge engine at oil change

Ex Bonanza Bucko

Well Known Member
I will have a new S-LSA RV12 in a couple of weeks. I will burn 100LL and use Decalin. I will change oil every 30 hours. But I can't find a step by step procedure for purging the oil from the engine to get all the lead out.

Can you give me that?

Thanks,
EBB
 
Before you drain the tank pull the prop through until you hear the gurgle noise indicating the oil has been returned to the tank. Then you'll just have what's left in the oil lines and a small residual in the filter and engine. If you also drain the lines you'll have to do the system purge to refill them. Check your ROTAX SBs because I think 25 Hrs is the recommended oil change frequency with 100 LL.
 
See latest Line Maintenance Manual page listed below. Oil change interval has been upped to 50 hours when using 100LL.

Effectivity: 912 Series Edition 3 / Rev. 1
05-20-00
page 16 January 01/2013
 
Good point!

See latest Line Maintenance Manual page listed below. Oil change interval has been upped to 50 hours when using 100LL.

Effectivity: 912 Series Edition 3 / Rev. 1
05-20-00
page 16 January 01/2013

Thank you John, this is an example of what VAF is about: helping others with information that otherwise might be overlooked.
 
If you use 100LL you can't purge the lead out. You can remove the tank and clean the bottom out and drain the oil, but that's it.

The Rotax SI912-016R6 says 50 hrs at the latest, but still recommends 25 hr. changes when using mainly 100LL. Sec. 3.3. The 25 hr. change is under notes.
After doing a pre-buy inspection today on a Remos with 700 hrs. that already had a top end done on Cyl. #2 and seeing all the lead on the tops of all pistons and in the oil tank I would stick to 25 hr. changes and make sure I use a fuel additive like Decalin as a lead scavenger. It isn't a cure all, but does help. For me tossing in a couple extra oil changes is way cheaper than paying the big bucks to send in heads to have lead removed and the gearbox has to go in at 600 hrs. verse 1000 hrs. to get the lead out of the clutch. If you can stay away from 100LL and use 91 oct. you will be far better off with future maint. and your pocketbook will thank you.

http://legacy.rotaxowner.com/si_tb_info/serviceinfo/si912i001r1.pdf
 
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See latest Line Maintenance Manual page listed below. Oil change interval has been upped to 50 hours when using 100LL.

Effectivity: 912 Series Edition 3 / Rev. 1
05-20-00
page 16 January 01/2013

Big John I trump you with page 4 September 2013:p

1b68f24e00714132e8e5fa02d138b080_zpsf27de779.jpg
 
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procedure for purging oil system

What I'm after is the procedure for purging the oil system on my 912ULS.

The Line Maintenance manual says in Paragraph 11.7 FLUSHING THE OIL CIRCUIT that the procedure is as follows:

1.Clean the oil tank (requires removing it an opening the oil system thus inducing air and thus requiring an oil system purge)
2.Install temporary oil lines for flushing. They must be fitted so that the oil cooler is not connected. The return line is routed to a separate, clean receptacle and not back to the oil tank.
3.Fill the oil tank with approx. 3L of engine oil
4.THE OIL LEVEL IN THE TANK MUST NOT DROP BELOW THE END OF THE SUCTION PIPE. OTHER WISE AIR WILL BE SUCKED IN
5.Turn the engine by hand in the direction of engine rotation to return the oil from the oil tank into the engine and into the collection container. The procedure is complete when no more contamination is observed.
6.Reinstall the oil lines.

My question about this is that this procedure seems to say that fresh oil must be added to the oil tank while the prop is turned until all the contamination is pumped into the tank. I wonder if anyone has done this and if that person can tell me how much oil must be added because it sounds like that might a lot of oil.

I would also like to know how much lead sludge I can expect to get out of the oil tank after 25 hours of operation on 100LL.

Thanks,
EBB
 
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I have a question about the possibility of air entering the oil lines. So...you do a oil change, add 3 gts. of oil to the canister, pull the top 4 plugs, start rotating the prop to get oil oil pressure. My question is: since oil can't be pumped back to the canister (because the plugs are pulled/no compression) can the canister get depleted of oil and can air then enter the system?

Rick.
 
It would be possible if you turned the engine long enough, but you will get oil pressure way before the tank was emptied (and if doing it by hand, your arm would probably fall off first).
 
To Purge or not to Purge

My understanding is that you don't need to perform a pressure purge if you don't let the oil drain out of the lines.

Please correct me if I am wrong but I thought the procedure was.
1. Burp engine
2. Drain oil from tank
3. If cleaning tank because you use 100LL
__a. Disconnect oil lines and keep them above the level of the tank
__b. Remove tank and clean
__c. Re-install tank & lines
3. Remove & Replace oil filter
4. Replace oil
5. Re-check oil level after rotating engine/circulating oil

So my understanding is that as long as you don't disconnect the lines and remove the oil filter at the same time, the oil will stay in the lines and a purge is not required.

Also, use a new crush gasket when re-installing the tank drain
 

Edit
I was looking through Line Maintenance today for something else and took a look at the tank cleaning procedure.... Confirmed that after tank cleaning it specifies a purge procedure be done.

I think Rotax specifies doing a pressure purge if the system is broken open for any reason. So I assume this would include removal of the oil tank.

But the recent post in this 1.5 year old thread wasn't asking about pressure purge. He was wondering about the chance of emptying the tank while turning the prop to get oil pressure (a requirement after an oil change, even if you don't open the system).
 
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In favour of mogas

Most Rotax 912 operators in Brazil (and there are many here) prefer using Premium 91oct mogas instead of avgas. My own engine is relatively new at some 350 hours, so there's not much I can say, but I know more than one owner that have run 912ULS to the TBO with no problems. Our premium mogas is 25% ethanol.
 
The manuals do say to do an oil purge after a tank cleaning because they assume you will drain oil from the hoses. If you want to do the purge by all means do it.

If done properly you don't need to do an oil purge and here is why.
COMMON SENSE NEEDS TO APPLY.

When you normally drain oil from the tank during a normal oil change all the oil in the tank including the two metal tubes inside and up to the fittings at the top of the tank all drain their oil. If you disconnect the oil lines on top they will be empty at the fitting. Either place these hose in an upright position or place a rubber stopper in them so no oil gets lost. Never rotate the prop once the system is void of oil or you will be doing a purge for sure. So long as you do not drain any oil out of the hoses you have not drained any more oil than a normal oil change. Once the tank is back in place and the fittings are attached then fill the tank. Now rotate the prop with the spark plugs in place approx. 20 times. This not only fills the oil filter, but will help charge the metal tubes and hoses to the tank. The key here is to lose no more oil in any hose line other than what is normally done in a standard oil change. Replacing the oil filter dry like we have to do introduces more air than a tank clean ever will so long as you do not lose any of the oil in the two hoses.

Rotax wants the purge because many don't understand the system and it covers them for any liability and makes sure the owner is in good shape should someone do it wrong.

Once you pull an empty tank off and break the lines you'll see what I mean about a normal oil drain dumping all oil up to and including the tank fittings.

As soon as I can get to it I will post what 100LL and using the wrong oil does to an engine. It isn't pretty.
 
As soon as I can get to it I will post what 100LL and using the wrong oil does to an engine. It isn't pretty.

I'm anxious to see this... My engine has 58TT with first 50 hours using 100LL avgas.

Now switched to 93 octane auto fuel and Mobil 1 Racing 4T 10W-40 Motorcycle Oil.

Piper J3
 
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At the ROTAX course the instructor said he has found the oil tank cleaning to be a pretty much useless task. Has anybody found anything bad while doing the tank cleaning? I'm at 400 hrs on the Hobbs and haven't touched the tank. Sometimes I think preventive maintenance becomes causal maintenance!
 
Another opinion - -

I never use 100LL. I use to take the tank apart. Never found anything, and stopped doing it. If you use 100LL, then it might be worth cleaning out tank. However, I do remove the cooler and drain it EVERY time. I also only change my oil at 100 hours since I only use premium auto fuel. There is too much dirty oil in the hoses and cooler to leave in my opinion. If you change more often, then it might not be that much of an issue. I am at 840 + hours now, and my system works well for me.
 
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At the ROTAX course the instructor said he has found the oil tank cleaning to be a pretty much useless task. Has anybody found anything bad while doing the tank cleaning? I'm at 400 hrs on the Hobbs and haven't touched the tank. Sometimes I think preventive maintenance becomes causal maintenance!

When I attended the Rotax class at Lockwood they said just the opposite, if you run 100LL. They showed pictures of lead sludge in oil tanks after just 25 hours of running 100LL. There was more than 1/4" of lead sludge in the bottom of the tank.

Their message was: When using 100LL change the oil at 25 hours and clean the oil tank. If you run auto gas, change the oil at 50 hours and you don't need to clean the tank.
 
When I attended the Rotax class at Lockwood they said just the opposite, if you run 100LL. They showed pictures of lead sludge in oil tanks after just 25 hours of running 100LL. There was more than 1/4" of lead sludge in the bottom of the tank.

Their message was: When using 100LL change the oil at 25 hours and clean the oil tank. If you run auto gas, change the oil at 50 hours and you don't need to clean the tank.

I was taught the same, and have also observed the same.
 
It's possible the instructor was referring to engines run on unleaded auto gas. He was definitely a proponent of unleaded gas.
 
I have run for periods of time on both types of fuel. Around home, I burn premium unleaded Shell 93 octane with up to 10% ethanol. When I fly cross country, I burn 100 LL with Decalin added.

There is definitely a film in the oil canister if I use much 100 LL. I can also see it in the oil as it tends to darken more quickly on 100 LL. I go 50 hours between oil changes if it is mostly auto fuel, and shoot for between 25 and 50 if it's a mix.

Bottom line, if you burn any 100 LL, I would clean the tank at oil change.
 
Here is a copy and paste from the Rotax forum. It is an eye opener for some. I guess I'll have to put these videos in my own file. This has all kinds of implications to this engine.
--------------------------------------------------------------------------------------

Perfect timing here for some videos.
Here is what happens when oil is left too long and the wrong type oil is used. The 912ULS engine is a 2008 with 83 hours TTSN.

You're going to love this. :eek:hmy::pinch:

https://youtu.be/gxUWvlAPYZk

https://youtu.be/DrjW3rnERGA

https://youtu.be/ioGzg1KPBUw
 
Roger,
What oil was used?
Was Decalin used in this engine?
This engine has 83 hours since 2008? - 83 hours in 7 years? When was the last time it was run before the oil change?
If the engine has 83 hours on it and report is the oil was run too long on 100LL, then it must have had the oil changed once - surely it didn't have the wrong oil put in from the factory or dealer, so assuming an oil change at 25 hours, that leaves 83-25=53 hours, just marginally longer than Rotax's allowable (granted, not prefered) oil change time.
Bad oil for 53 hours over what period of time? When was the oil changed the first time? I'm trying to figure out if this engine sat with bad oil for a log time or if it ran bad oil for only a short time?
It is useful for all of us Rotax operators to know the full extent of the operating conditions in the videos. Rather than ask Roger a zillion questions, maybe Roger would just post the history of the engine in as much detail as he has and we can all share in the information and knowledge.
 
Thanks, Piper J3, here are some excerpts from the Rotax Owners post by Lee. Go to the cited reference to see the entire post, or Roger (Sink) can repost if he wants to.

"The only oil listed was Valvoline at 25 hrs. back in 2009. No other entries in the books other than each year it said it was found to be in a safe condition for operation. There were many things wrong here and this was just one of them. So the oil may be as old as 6 years, no one knows and the oil maybe auto full synthetic. It will not suspend the lead and isn't a motorcycle oil that will protect the gearbox....

Even with the years in age the lead fell out of solution in 58 hrs."

This situation reminds me of the aphorism, ""Great cases like hard cases make bad law" declared Justice Oliver Wendell Holmes, Jr. "

That is to say, there is really little to be learned from a case where an owner and mechanic so neglected and abused the system. It really says nothing about what most of us will encounter as owners, operators or mechanics when it comes to 100LL and changing the oil every 25 or 40 or 50 hours.

Let's suppose you took a 4 week a tour of the U.S covering 50 hours and used 100LL all the way. Would the oil look like that in the video Lee posted? I doubt it, but that is the question. Using the above example only speaks to a particular and extreme case of abuse and only tells me to not let my engine sit for 8 years.

It would be interesting to see what engine operations were conducted over the 7 year span, if any.

It would be interesting to see the credentials of the mechanic - was this an E-AB owner? A LSMR-A? An A&P?

This is kind of like showing a picture of a baby that was tossed off a 5 story building as a reason to not toss your baby to the ceiling and catch it in your living room.
 
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Just cleaned my oil tank for the first time in 788 hours. :eek: I've run 98% unleaded auto fuel. Looked great with a small amount of sludge in the very bottom of the tank. Won't be doing it again any time soon.:D
0E0F7184-4DA4-48CF-917A-6E999FE78B16_zpsvhb2ab6w.jpg

308B16B1-67D5-4AA9-AE20-54740FDEE5B2_zps2oyfkkge.jpg
 
Hi John,

Nice job.

If using unleaded fuel and doing the appropriate oil changes then tanks tend to remain quite clean. Using 100LL all the time and regular extended oil change intervals can certainly cause build up down in the bottom and on the screen. Yours looks like I would expect with unleaded fuel use and good maint. practices.
 
John,

Since you are burning auto gas are you using a 50 hr oil change interval? I'm interested because that's the interval I use and I burn Auto gas >90% of the time.

Rich
 
John,

Since you are burning auto gas are you using a 50 hr oil change interval? I'm interested because that's the interval I use and I burn Auto gas >90% of the time.

Rich

Yes! After watching those youtube videos I got motivated to clean the tank. ;)
Now that I've done it all the mystery has gone out of the procedure. I did order a new o-ring that goes around the rim since mine hasent be done for some time. that O-ring is a little expensive, $32.00. I will probably do it every 200 hrs or so. I like a clean engine.:p
 
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Oil change 3L of oil or less?

Burping then draining....to change my oil and filter I am finding I need only 2.6L of oil to get to the mid point of the dip stick. Is this common?
 
Burping then draining....to change my oil and filter I am finding I need only 2.6L of oil to get to the mid point of the dip stick. Is this common?

Yes

Burping doesn't drain the entire oil circuit. there is still some oil in the oil cooler and pick-up hose.
 
Always appreciate when others post pictures on here so I'll offer a couple as I wrap up my annual. First is the magnetic plug which was last removed about 120 hours ago. (change oil about every 35-40 hours with minimal leaded fuel use) I confess that I'm lazy and don't remove the magnetic plug at every oil change. (Plug is safety wired to a point below the oil filter so to access it the lower cowl needs to be removed.) I do have the oil analyzed and open the filter so I didn't suspect any problems. Looks fairly clean to me considering the hours.

2z5ric8.jpg


These are my spark plugs. First picture is at last year's annual when they had just under 100 hours on them. Engine was running very smoothly. Since they looked clean, I just checked gaps and reinstalled. Second picture are the same plugs now with 227 total hours on them. Several of them had gaps that were out of tolerance per ROTAX manual. Engine was still running very smoothly nonetheless. Yes they are cheap and will likely replace every year going forward.
svkok3.jpg

30sav51.jpg
 
First is the magnetic plug which was last removed about 120 hours ago. (change oil about every 35-40 hours with minimal leaded fuel use) I confess that I'm lazy and don't remove the magnetic plug at every oil change.

Rotax only recommends that the magnetic plug be inspected at every 100 Hr inspection (it is on the check list).
 
As others have said in this thread - purging the systems _anytime_ the system is open is what Rotax requires. It's no big deal and should be in the installation manual available from Rotax to download. The big concern is having the lifters bleed down.

I also just finished the maintenance class and cleaning the tank was _not_ recommended. The analogy used was that no one would pull the sump off a lycon or conti to do an oil change.

The clutch in the prop gear housing is what's going to get really leaded up anyway and there's no way short of rebuilding the gearbox to get the lead out - which is why it has a shorter service interval when running avgas more than 30% of the time.
 
I went right to the Rotax expert for this question.

You are supposed to check the magnetic oil plug every oil change per Rotax ASB-912-051.
You don't "PURGE" and engine at the oil change, you "VENT" it. The oil purge is only done when you dump the oil out of the oil hoses, oil cooler or like when the Rotax 5 year hose change is performed. This requires the inlet hose to the tank to come off, that port on the tank to be blocked and air pressure applied to the tank and then the prop rotated to "RE-FILL" the entire oil system, remove air and make sure the tappets have oil..

When you do an oil change all you do is vent the system. It just helps prefill the oil filter and remove some air back to the tank which is the only engine vent to the atmosphere.

The manual says to clean the oil tank every 200 hrs. If you use all 100LL this is important. Not so much so if all you use is 91 oct. Lead accumulates at the bottom of the tank and around the bottom of the screen. There is no good reason not to clean a tank and that comes right from Rotax. When I questioned this this is the video they sent me to watch. They told me using the wrong oil will cause this mess and running too long an extended oil change interval.

https://www.youtube.com/watch?v=ioGzg1KPBUw

https://www.youtube.com/watch?v=gxUWvlAPYZk

If all you do is remove the top two oil fittings on top of the tank and do not let them hang and lose any oil then all you have to do is replace it, fill it and do a standard oil change "VENTING". The reason told to me is that when you open the bottom oil tank drain all the oil up to and including those two fittings drain out anyway and none comes from the hoses. I just use a plug in the hose ends while I clean the tank and I haven't lost more than a drop of oil.

The gearbox does not get rebuilt at the 600 hr. mark from using 100LL more than 30% of the time. They told me that if you use 100LL a lot then usually by 800 hours the clutch is pretty clogged and even though we can't tell the difference it probably would function properly from all the lead. The overload clutch comes out and sent to a service center and it gets disassembled and cleaned due to lead fouling. The other parts are washed off, but should be fine. I was told when they re-assemble it they usually replace the bellville washers and reshim to its proper spec.
 
For new engine first start, or when opening / replacing oil hose hoses ? follow Rotax/Vans instructions.

For oil change?

  • Warm engine
  • Remove cowling
  • Burb engine several times to get all oil from crankcase
  • From this point on ? DO NOT TURN ENGINE
  • Drain oil from tank
  • Remove / replace oil filter (you can pre-oil filter ? I don?t)
  • Remove / inspect gearbox magnet plug
  • Pour in 3 liters Aeroshell Oil Sport Plus 4
  • Engine is ready to start ? monitor oil pressure
 
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