facthunter Posted June 20, 2015 Share Posted June 20, 2015 That is unusual but you can never rule these things out It's more common with Radials as they have a pretty inadequate sump for the oil to collect in, and it runs into a cylinder that is inverted (or nearly so). Turning a motor over in a forwards direction should pump a bit of oil into it. Turning it backwards will usually introduce some air into the oilways and may affect vacuum pumps (if fitted) so don't do it (although it is part of the priming procedure on a DH 82) so there are exceptions. The Rotax 912 is geared down so the engine turns more times than the prop so has a different feel than a direct drive engine. If you pull the engine over slowly and steady the hard spots should all feel equal resistance. To burp the engine moving it slower is often more effective especially with a new motor. Nev Link to comment Share on other sites More sharing options...
DGL Fox Posted February 3, 2019 Share Posted February 3, 2019 Hi All, I seem to have a peculiar problem, I have just done a 50 hr oil and filter change and when the engine is cold I do my normal burping procedure and when I check the oil level it is way above the high level oil point on the stick, no matter how many times I pull it through and burp it I can't get it to come down to half way on the flat of the stick. So I go and start the engine and let it run for a few minutes, oil pressure is good and I turn it off and go and check the oil level and it is perfect....when I check it hot the levels are right...so strange that I now can't get it show the correct level on the stick when I burp it cold....any ideas... maybe I did something when I changed the oil and filter? Link to comment Share on other sites More sharing options...
spacesailor Posted February 3, 2019 Share Posted February 3, 2019 All motor engines when sat idle for a length of time, will allow All the oil to drain down to the bottom sump. Also hopefully NOT, emptying your oil-filter. Once run for a few seconds, lots of said oil is coating the inside walls & underside of the piston's, thus lowering the dipshit level. spacesailor Link to comment Share on other sites More sharing options...
IBob Posted February 3, 2019 Share Posted February 3, 2019 Hi DGL, there may be some misunderstanding here: The Rotax is a dry-sump engine , with the bulk of the oil held in the oil tank. However, after running, residual oil in the engine will drain down to the sump of the engine. With oil still in the engine, you cannot accurately check how much oil is in the entire system. Futhermore, if large amounts of oil pond in the bottom of the engine for whatever reason, the engine may be damaged on startup. For this reason, the standard drill is to manually turn over the prop until a gurgle is heard from the oil tank: this indicates that the engine sump is now empty of oil. (the gurgle or burp is the oil pump passing air because all the oil is gone from the engione. With all the oil back in the oil tank, level can now be checked. And the engine can be started without risk of damage from excessive oil. So. When burping the engine cold, the oil level in the tank will go up. If, on burping, the level is too high, then there is too much oil in the engine. 1 1 Link to comment Share on other sites More sharing options...
facthunter Posted February 3, 2019 Share Posted February 3, 2019 A near new engine where the rings have seated in perfectly is hard to burp. You have to deliberately turn it slow to force the blowby to be significant or it takes a long time. Also this is an intermittent thing whereas when the engine's running it's more constant. Pushing oil up a pipe with a pressure differential provided by a gas is not a terribly good idea. IF the bore is large a bubble of gas is constantly allowing oil to get past it, moreso when the oil is thin. the effectiveness of it is not entirely predictable and you are putting a positive pressure through the entire engine to achieve it. A positive displacement pump like the pressure one but bigger is normal for scavenging oil. In my view this "trick" system is not worth the trouble, but you are stuck with it. If you get inverted or some negative "G" you will empty a lot of oil fast out of the standard oil tank. Nev Link to comment Share on other sites More sharing options...
Downunder Posted February 3, 2019 Share Posted February 3, 2019 Hi All, I seem to have a peculiar problem, I have just done a 50 hr oil and filter change and when the engine is cold I do my normal burping procedure and when I check the oil level it is way above the high level oil point on the stick, no matter how many times I pull it through and burp it I can't get it to come down to half way on the flat of the stick. So I go and start the engine and let it run for a few minutes, oil pressure is good and I turn it off and go and check the oil level and it is perfect....when I check it hot the levels are right...so strange that I now can't get it show the correct level on the stick when I burp it cold....any ideas... maybe I did something when I changed the oil and filter? Your engine is overfull. As others have said, you need to leave the engine off for a while to let the oil drain down back to the tank. Burp then check. I personally don't top up until it is consistantly low (over about 3 checks) unless it is below 1/2 on the stick, as it can vary a bit. When I change the oil and filter, I fill tank to top level. Start and run engine. Leave overnight. Recheck. Level will be lower as oil has had to fill oil filter. Top up and fly. Link to comment Share on other sites More sharing options...
DGL Fox Posted February 3, 2019 Share Posted February 3, 2019 Ok but why is the level ok when it is hot? Link to comment Share on other sites More sharing options...
IBob Posted February 3, 2019 Share Posted February 3, 2019 Because some of the oil is then remaining in the engine....until you burp it. Link to comment Share on other sites More sharing options...
DGL Fox Posted February 3, 2019 Share Posted February 3, 2019 Ok great..thanks for your comments..I will have a look at the oil levels.. David Link to comment Share on other sites More sharing options...
Blueadventures Posted February 3, 2019 Share Posted February 3, 2019 Ok great..thanks for your comments..I will have a look at the oil levels.. David Hi David. I agree that it sounds like over full. How do you change the oil and determine the refill amount? (I drop mine into a measure jug and when filling with new oil I put that amount plus a little extra for the oil filter amount; this way I always finish up at the same level. I aim for 2/3 up the flat on the dip stick.) I like your flying stories about your recent flights; we have had a long spell of ordinary weather so looking forward to it clearing up and fitting in some nice flights around the place. Cheers Mike Link to comment Share on other sites More sharing options...
spacesailor Posted February 3, 2019 Share Posted February 3, 2019 A little Gem I found out about !. The dipstick has only two mark's on it, if your level is around the bottom mark you have Minimum oil, (and things get hot as oil is used for cooling) And Don't fill to the top mark as it means MAXIMUM,do not exceed. 3/4 should be marked, but isn't, so keep it between 1/4 and 3/4 OR the "Half" 1/2 mark that's not there !. A lot of people are going to oppose this as they've always filled to Maximum, giving longer time to an oil burning engine, between Topups. spacesailor Link to comment Share on other sites More sharing options...
Blueadventures Posted February 3, 2019 Share Posted February 3, 2019 A little Gem I found out about !. The dipstick has only two mark's on it, if your level is around the bottom mark you have Minimum oil, (and things get hot as oil is used for cooling) And Don't fill to the top mark as it means MAXIMUM,do not exceed. 3/4 should be marked, but isn't, so keep it between 1/4 and 3/4 OR the "Half" 1/2 mark that's not there !. A lot of people are going to oppose this as they've always filled to Maximum, giving longer time to an oil burning engine, between Topups. spacesailor If over full it's spat out the vent pipe, that's why I aim for 2/3 rods as my max. Cheers Link to comment Share on other sites More sharing options...
skippydiesel Posted February 3, 2019 Share Posted February 3, 2019 We all love the Rotax BURP & lubrication debate - Me ? I change oil in my 912ULS (800 hrs) every 50 hrs (cause it makes me feel good). I use 3 litres of AeroShell Oil Sport PLUS 4 (G.. what a mouthful). This usually takes the cold level, to slightly above max on the dip stick. In 50 hrs it will drop to max. I have never actually measured the old /wast oil, but I drain into a graduated automotive style drain bowl, estimate my oil usage to be about 150-200 ml, well within allowable specifications. On the oil level indication (stick) - it seems to me that variations in oil reservoir/tank location (particularly hight above crank case) will influence the indication. This can be the case even between aircraft from the same stable & model. BURPING - a deeply satisfying activity no matter how practices. With the Rotax, I do it when cold for all of the aforementioned reasons. I also do it several times between engine starts - I believe/hope this gives me the best indication of quantity, as to do it once will leave considerable residue slowly draining to the bottom of the crank case (not in the reservoir/tank where the dip stick is). I also hold with the idea that this is pre lubricating my engine innards (for less ware on start up) and removing any chance of hydraulic lock in the event of oil "bleeding" into a combustion chamber - this requires a few more than the minimum turns to BURP - I like to do several complete rotations of my engine (deeply spiritual). 2 Link to comment Share on other sites More sharing options...
spacesailor Posted February 9, 2019 Share Posted February 9, 2019 " If over full it's spat out the vent pipe, that's why I aim for 2/3 rods as my max. Cheers " Why over fill to above the max, if you throw oil over that lovely clean aircraft,? This usually takes the cold level, to slightly above max on the dip stick. In 50 hrs it will drop to max. " Just throw a few Dollars into the coffee/biscuit tin. LoL If you start with just a little less oil, it could be Added at 25 hours IF needed. So 2.75 litres into the motor & a bit for the oil-can, Several rotation's of the engine, ! TRY the 1/2 VW, 30 rotations to pump the oil pressure up to readable . then put the spark-plugs back in. When people watch, you just say, "winding the rubber band". spacesailor Link to comment Share on other sites More sharing options...
alf jessup Posted February 9, 2019 Share Posted February 9, 2019 I usually burp mine after shut down for the day as the oil is hot and flows easier back to the can, then just check it before next flight, been doing it this way for the last 1500 odd hours behind a Rotax and never have had an issue. Also after shutdown I open the cowls to let the latent heat dissipate and not bake my ignition modules , this is while I fill out the paperwork, log book, wipe the bugs off and put the cover on, just a few quirky things we probably all do a bit different. Link to comment Share on other sites More sharing options...
DGL Fox Posted February 9, 2019 Share Posted February 9, 2019 Thanks everyone for your advise...and yes it was the overfull, somehow I didn't get it all out when I did the service and when I checked on how much oil it would need with a filter in the Rotax manual I must have put in to much...anyway lesson learn't...I took some oil out (about 600 mill) and all is good... David 1 Link to comment Share on other sites More sharing options...
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