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Ex Bonanza Bucko

Well Known Member
I heard that if you check the oil AFTER flying it is not necessary to burp the engine before flying the next day....or hours later. If you agree with that please tell me.

Then, if the above is true, why is the oil not in the oil tank in the morning, or after some hours, if it was there for the oil check after flying?

I guess I need to know what the purpose of burping the engine is....and if it is more than just to check the level of the oil in the tank.

Thanks....I'm a new RV12 owner...learning.

EBB
 
To accurately check the oil level. It requires fewer turns of the prop immediately after a flight than if you let it sit overnight. Check after a flight for the convenience, and if you have no oil puddle on the floor before the next flight, the oil is still in there.

The ROTAX uses VERY little oil between changes. The engine compartment stays clean.

As you turn the prop, stop as you feel compression. The compression pressure drives the oil into the tank, not the turning of the prop and thus the oil pump.
 
Use the starting carb ("choke") on the first start of the day and not on subsequent starts. To use it, have the throttle all the way out. It will start and you can slowly put the "choke" in and as the engine loses rpm, replace it with the throttle. When the engine is warm, just start with the throttle slightly cracked.
 
EBB,

As a fellow RV-12 newbie (and soon to be owner of new SLSA) I found this a while back and thought it might answer your question.
For me I thought it was a good explanation. I can't remember where I found it.


If you pull the dipstick and the oil level is where it's supposed to be before flight then you have CHECKED it. If you want a more accurate reading then you can 'burp' it. But consider, IF your dipstick shows oil is where it should be then you can burp away but the vast majority of the oil is in the tank.

If the oil level is LOW on the dipstick then you can burp to get the oil back into the tank for a more accurate reading. Also, you should burp before adding oil otherwise you could overfill.
Hence if you own your plane and you do all the servicing, at the end of the flight you can burp when the warm oil is easy to move. Take a dipstick check and unless you return to a large puddle of oil underneath and suspect a leak then a re-check of the dipstick (in an already burped tank i.e.. the oil is already back in the tank) will confirm what you already knew (as in CHECKED) if the oil is in the correct range.
If you are a renter and don't know what the oil level was on previous flights then burping EVERY time is more appropriate.
Note: this is a CHECK not a DO unless you are a 'burpaholic' and therefore...burp away!

The following is a great account of the burping, oil checking, oil servicing scenarios. Note: burping is also done before an oil change and again, before adding oil to prevent overfill.

Consider:- the purpose of checking the oil and the need for the pilot to get an ACCURATE reading, not just burping for burping's sake.

Rotating Propeller for Checking or Changing Oil
- Rotating the propeller pumps residual oil from the engine into the oil tank so the oil tank is completely full. This would be required for two situations:
o You are getting ready to change the oil and you want to make sure all the oil is in the tank before you drain it, or
o You checked the oil and it reads low on the dipstick. Before adding oil, you rotate the propeller to get the oil up to the calibrated level for an accurate oil level check. Do not add oil before rotating propeller or you could over fill tank.
- Facing propeller, always turn prop to top left/counterclockwise. Never turn propeller clockwise or you draw air into the engine valve train which is bad for the engine.
- Important process before accurate oil check or oil change is to ?burp oil system?
o Take oil cap off and put where you will never forget to put it back on
o Pressurize with propeller/engine compression stroke and listen for gurgle out of oil tank (burp). Some installations can take 20 rotations of the propeller to achieve the burp. Be patient.
- Having burped tank, oil is returned to tank for accurate measurement and changing.
- Use/update to square handle dip stick
- When checking oil, oil level should fall within the flat portion of the dipstick.
- Assure cap is properly secured to avoid oil loss during flight.
 
Bill H mentioned this in post #2 above, but it is worth emphasizing. It is NOT the oil pump that moves the oil (not much anyway) from the engine to the oil tank. It is air leaking past the piston rings that pressurizes the crankcase and pushes the oil down and out to the oil tank. As a new RV-12 owner, I turned the propeller rapidly to purge the crankcase. Later I learned that it is much easier to turn the prop slowly, stopping as each piston reaches top dead center of the compression stroke. You can feel this as the prop becomes harder to turn. Wait at the top of each compression stroke for a few seconds to let the air leak past the piston rings. Doing it this way requires fewer turns of the prop, making the job much easier.
Like, Top Cat said, it is only necessary to burp the engine before adding or draining oil, or to verify a low dip stick indication. It doesn't hurt anything to rotate the prop before engine start just to make sure it feels right.
Joe Gores
 
So I guess what all this very good info you have given me means is that the ONLY purpose for the "burp" is to check the oil level. If that is so and 1.) I just changed the oil and I know how much is in the engine and 2.) There is no oil puddle on the floor I do not need to go through the burping hassle.

Is this correct?

EBB
 
Read the ROTAX Line Maintenance manual (Page 49 - Section 11.2 - Step 8) and view the Rotax-Owner videos regarding a standard oil change. Following a standard oil change, you need to hand-crank the engine in the normal direction of rotation @ 20 turns to aid in "refilling the oil circuit".
 
As David points out rotating the prop about 20 times helps pre-fill the oil filter. This new filter can not be pre-filled off the engine like the older types because of the check valve in it.

The burping of the engine should only be used as a guide to oil level because it can lie. If you rotate your prop and don't hear the gurgle then there is still oil in the bottom of the crankcase. Sometimes you can turn the prop 4-6 revolutions and it gurgles and sometimes it takes 20. If you look on the dip stick when it's cold and the oil level is 1/2 to 3/4 full it will only become higher on the stick if you burp it.
 
Before a burp, the oil level on my dipstick can be one inch lower than after burping. It can easily be below the flat spot on the dipstick.
 
That does happen to some and then sometimes it isn't that way. That just means you have more oil in the bottom of the case verses someone else and it usually takes more prop rotations to get it all pumped back to the tank. It used to be because of how high the oil tank was mounted compared to the engine and if it was the older oil filter. Kitfox had this issue for a long time with the old filters and a high tank mount.

Prop rotation to gurgle is a good guide, but isn't an absolute indication. It can mislead you towards the low side. Then someone adds a little too much oil and next thing the oil is flowing out the vent tube on start up. Doesn't hurt anything other than making a huge mess. I tell all my clients if you think it is a tad low then before you add more oil start it up for a couple of minutes and re-check it. So long as the oil is on the flat area of the dip stick it won't hurt anything. Several years back the oil level used to be 30% lower. Rotax raised the level with a new dip stick because of oil foaming with a little bit too low a level then the system sucked in air.
 
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