Engine breathers on PA-30

[William Menne]

My PA-30 seems to be using more oil than it should. The spark plugs look OK and don't indicate excessive oil burn. The exhaust appears a normal grey. I do have some leakage around the cylinder head oil return lines, but this doesn't appear to account for the oil consumption. I'm focused on the oil breather lines and am looking for advice. Do the breathers have a history of creating suction? and should I be looking at oil-air seperators?

Thanks!

[N3322G]

Hi William,

Noticed this is your first post - welcome to the Forum.

Just guessing the PA30 is new to you - if that is the case and you've looked at the usual high oil consumption suspects, perhaps it is due to how much oil you are trying to carry. I say this based on experience. I'm sure others will chime in.

Right now my PA39 averaged 18 hours per quart over the past year as I just calculated that when I sent the oil sample in for analysis. No debris in oil filters, about 600 hrs SMOH. I keep the oil about 6 qts with dipsticks re-calibrated for each engine as the canting does make them read differently. We only re-fill when the oil is just below 5 or 5.5 if there is a 10 hr trip coming, we'll put in 0.5 qt per side so we don't have to mess with it on a ramp somewhere.

Specs say the engines will run fine down to 2 qts. The top of the dipstick says 8 qts and some shops take that as the proper fill quantity. My experience and that of my Mom's, the previous owner, says the oil will blow out in flight and be wasted rather quickly.

FWIW that's 42 years of oil filling experience on this twin. Hope it helps in your situation. I'm sure others will post and kindly post if you find something else as the root cause of the problem so we can all learn.

[William Menne]

Yes, I am a new TC owner.

I have considered that I may be 'overfilling' the engine and that I'm not letting it find it's natural level. The right seems to have more of an issue with this than the left side and may very well be due to the right dipstick reading one quart lower than the left because of the engine cant when the same amount of oil is added after an engine drain. (The dip sticks are identical length on both engines, so I should probably consider recalibrating the right side stick to read what is actually in the engine. For now, I just know there is one more quart in the engine than what the right dipstick says.)

I've been filling to 6 quarts indicated which quickly drops to 5 quarts on the left and 4.5 on the right (which is really 5.5 in the right engine). The oil drop is within 2 hours. I have been limiting myself to shorter trips while I watch this.

Could I just be too cautious about this???

I would be interested if anyone has experience with oil air seperators in the PA30 if nothing more than a way to keep the belly clean.

[Kristin Winter]

An air/oil separator will just mask a deeper problem. If you are getting a lot of oil out the breather, it is likely either that there is too much oil in the crankcase or you are having excessive blow by the rings. How many hours are on the engine? Are the cylinders chrome or steel?

I would recommend trying to calibrate your dipsticks. I did this by grinding off the marks and using a stamp set, marked it at 2, 4, and 6 quarts. I would try flying at five quarts and see if that materially changes the oil consumption. My airplane wants to blow out any more than about 6 quarts, so I file to 6 and add at 5.

Kristin

[Jim Menconi]

Even though my experience with the Comanche aircraft is limited, I have good experience with the 0320 engine. I owned a Maule for 14 years with an 0320 and found the same problem existed if you fill over 6 qts. Don't know why but 5.5-6 qts seems to be the number that works. Everything over that will just blow out.

Jim

[Zach Grant L1011jock]

Lycoming rule of thumb...12 qt capacity blows to 9, 8 qt capacity blows to 6. If you don't want to clean off the belly, start with the lower quantity, and then you will see what it is really burning!
-Zach

[William Menne]

Just an update on the actual cause - oil return lines were leaking excessively. Surprising part for me, it was not obvious how much oil was leaking as there was little oil in the cowling or on the belly. Thanks for all the advice!

[Jim Worley]

William,
How did you determine that the oil return lines were the culprit? Thanks.

v/r
Jim

[William Menne]

We couldn't identify any other oil leak, tightened the connections, fly the plane and saw greatly reduced oil consumption. No other changes were made.