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Oil quantity

P

P51krause

Member
Try again. My previous thread is somewhere in internetsphere. Anyway, I replace my oil lines on the 912 uls. Burped (sound different than before) and it looked low so I added half a quart. Flew it and it ran great. I’ve been busy the last few weeks so I haven’t flown since. Went to fly yesterday and after burping (again just a different gurgling/ burping sound than before) and the oil quantity was too high. It was beyond the hole for the dipstick. I drained some out and rechecked the quantity and it looked good. I ran it for about a half hour, oil pressure was good, and it ran nice. Shut it down and burped it again and rechecked the oil quantity and it was again way too high. Above the hole for the dipstick insert. What am I missing? Any thoughts as to why it would be too full? Thanks in advance
 
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My guess is if you way over filled it when you changed your oil, you may not be getting it all to flow into the tank when you burp it, which may also explain the unusual burping sound. I’d keep burping and draining excess oil until it reaches the correct level. You know it has to level out at some point.
 
When you replaced oil lines... did you follow Rotax procedure to ensure no trapped air in hydraulic lifters?
 
Piper J3 said:
When you replaced oil lines... did you follow Rotax procedure to ensure no trapped air in hydraulic lifters?
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I’d have to assume so. I had a mechanic do the oil line change since I was unavailable to do the 5 year change with my work schedule. So I trust him, he’s down great work before so I have no doubt he did that procedure. I’ll call and verify, but I’m almost certain he did. Good point though.
 
Bob Y said:
My guess is if you way over filled it when you changed your oil, you may not be getting it all to flow into the tank when you burp it, which may also explain the unusual burping sound. I’d keep burping and draining excess oil until it reaches the correct level. You know it has to level out at some point.
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I will burp some more and empty till it’s within the dipstick mark. I drained out a half quart yesterday, and after checks it. It was within the dip stick marks. Ran it for 30 min and checked it again (burped it and checked) and again it was above the fill line on the dipstick, in fact it was just above the hole where you insert the dipstick, so way to high. Anyway I’m checking with the mechanic to see if there is something else I’m missing, or he missed, but thought I’d ask this group. It does run great, and oil pressure is good. I see no blow off or any oil leaks anywhere. Thanks for the suggestion and I’ll see what works
 
Hard for oil to hide anywhere in a 912 engine except the crankcase. It may be possible that prior burping was not sufficient to get all of the oil out of the crankcase.

Also, the procedure for removing air from the oil system is called "purging the lubrication system". It should be done anytime the oil system is opened and air enters the oil lines or cooler (eg, when replacing hoses). If, during the purge, the drain line from the crankcase is not kept below the level of the oil outflow port on the bottom of the engine, then oil will accumulate in the crankcase. Ask me how I know...
 
If after you burp the system with a cold engine you find that the oil level appears quite low but there is no oil on the belly, do not start adding oil.
If burping can get the level up to the minimum mark on the dip stick, go fly.

Then burp and check the level again after the flight.

Reason - If the airplane has sat some and a lot of oil has drained from the tank into the engine, checking the level with the engine cold will not be accurate because the thick oil will not all flow out of the engine case with just one or two burps of the system.
If there was a lot in the engine, it takes quite a while for the thick oil to flow to the outlet to get pushed back up to the tank by crank case pressure.
When the oil is hot it is much lower viscosity and will flow easily.
Checking while hot is the only way to get a truly accurate measurement of the oil level.
 
Agree 100% with Scott.

I fell into this trap when I was new to Rotax coming from Lycoming.

Now for preflight I check the hangar floor, the cowl (inside) and do a cold burp to see if there is anything on the stick (usually reads a little low). Then post flight, accurately check on level ground, hot, that its exactly at the 3/4 mark, seems to be the thing that works best for my 12.
 
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