Oil Consumption issues - IO360 B1B - 61 Travel Air

[retailguy]

Cross posted to Beechtalk...

Need some advice and suggestions here.

Basics:

1961 Beechcraft Travel Air (Left Engine if that matters)
IO-360 B1B - converted to Bendix fuel injection in 2009.
1997 overhaul - ~900 hours, no cylinders have been off plane since overhaul.
chrome cylinders, iron rings.

quick backstory. Flew this plane 70 hours from January until April when it went in for annual. Probably put a quart of oil in each 10 hours of flight but was so insignificant none of us really tracked it.

Coming out of annual it has used a quart of oil consistently about every 3 or 4 hours. It has done this for 50 hours since June 1st when we got it back after annual and some avionics upgrades.

Yesterday, we pulled the 4 lower spark plugs. 3 had carbon deposits, no sign of oil. One, (cylinder #3), was wet, and showed carbon deposits as well. At that time we didn't take the top plugs out and began to suspect that the oil control ring was stuck or broken.

This morning we flew about 50 miles to a friends hangar who had a boroscope and some compression equipment. Took the top plug out of cylinder and found it dry with no sign of oil at all. Needless to say we were surprised. With the kind of oil consumption we have, we expected it to be wet, it wasn't, and didn't look like it had ever been wet.

Compression check - 78/80.

Pulled other three top plugs at that point. No issues. All 4 looked identical, no carbon deposits, no oil, exactly as you'd expect plugs to look.

Boroscope on cylinder #3 was unremarkable. No scoring, no obvious issues anywhere. Looked perfectly normal.

What we know:

- consistent oil consumption
- oil on underside of wing behind exhaust pipes and oil breather
(cleaned it off, back 12 hours later)
- no oil smoke on startup
- runs well, no issues with performance
- We changed the oil ourselves 12 hours ago, did not have it analyzed, did not find anything in oil or filter.

Thoughts as to what we should do next?

 

[RotorAndWing]

Cross posted to Beechtalk...

Need some advice and suggestions here.

Basics:

1961 Beechcraft Travel Air (Left Engine if that matters)
IO-360 B1B - converted to Bendix fuel injection in 2009.
1997 overhaul - ~900 hours, no cylinders have been off plane since overhaul.
chrome cylinders, iron rings.

quick backstory. Flew this plane 70 hours from January until April when it went in for annual. Probably put a quart of oil in each 10 hours of flight but was so insignificant none of us really tracked it.

Coming out of annual it has used a quart of oil consistently about every 3 or 4 hours. It has done this for 50 hours since June 1st when we got it back after annual and some avionics upgrades.

Yesterday, we pulled the 4 lower spark plugs. 3 had carbon deposits, no sign of oil. One, (cylinder #3), was wet, and showed carbon deposits as well. At that time we didn't take the top plugs out and began to suspect that the oil control ring was stuck or broken.

This morning we flew about 50 miles to a friends hangar who had a boroscope and some compression equipment. Took the top plug out of cylinder and found it dry with no sign of oil at all. Needless to say we were surprised. With the kind of oil consumption we have, we expected it to be wet, it wasn't, and didn't look like it had ever been wet.

Compression check - 78/80.

Pulled other three top plugs at that point. No issues. All 4 looked identical, no carbon deposits, no oil, exactly as you'd expect plugs to look.

Boroscope on cylinder #3 was unremarkable. No scoring, no obvious issues anywhere. Looked perfectly normal.

What we know:

- consistent oil consumption
- oil on underside of wing behind exhaust pipes and oil breather
(cleaned it off, back 12 hours later)
- no oil smoke on startup
- runs well, no issues with performance
- We changed the oil ourselves 12 hours ago, did not have it analyzed, did not find anything in oil or filter.

Thoughts as to what we should do next?

Have you checked the crank case breather tube and confirmed it's clear? It's summer in the US and all kinds of bugs love to make nest (dirt daubers) especially if the plane was sitting while undergoing an inspection.

 

[JHW]

many travel airs have wet vacuum pumps and an oil sep, if yours does that's another place to look

 

[retailguy]

Have you checked the crank case breather tube and confirmed it's clear? It's summer in the US and all kinds of bugs love to make nest (dirt daubers) especially if the plane was sitting while undergoing an inspection.

It's been sitting outside in a T cover as we wait for a T hangar to come available. I will check this. Thanks!

Can you help me understand if this was plugged where the oil would go and what this would cause?

many travel airs have wet vacuum pumps and an oil sep, if yours does that's another place to look

We will check this as well. Thanks!

 

[RotorAndWing]

Lycoming Trouble Shooting Guide

 

[frfly172]

Check the breather tube,and the wet pump. My 59 Travelair had very low oil consumption ,did have to change out one of the pumps.

 

[Henning]

Your front crank seal can cause a lot of oil to blow out the breather. What happens is high air pressure builds behind the prop and blows into the crankcase through the seal blowing out the breather taking oil with it. 1997, those seals are old, not an expensive fix.

 

[EdLarkin]

Read Mike Busch's article in EAA magazine (about 4 or 5 months ago) regarding oil. It's either burned, pumped overboard or leaked into engine compartment.

He discusses each in detail.

 

[Norman]

Your front crank seal can cause a lot of oil to blow out the breather. What happens is high air pressure builds behind the prop and blows into the crankcase through the seal blowing out the breather taking oil with it. 1997, those seals are old, not an expensive fix.

Right on. Had one of those drive me nuts once. Turned out someone had installed the wrong seal and there was a 1/16 gap between the seal and the crank.

 

[retailguy]

Your front crank seal can cause a lot of oil to blow out the breather. What happens is high air pressure builds behind the prop and blows into the crankcase through the seal blowing out the breather taking oil with it. 1997, those seals are old, not an expensive fix.

Is there anyway I can test this other than just having the seal replaced? Reason behind asking, is there is no clear cylinder that is causing problems, yet it has symptoms of having excessive pressures. There is lots of oil under the left wing which may indicate oil leaving the engine through the breather tube.

Would this seal increase crankcase pressure?

 

[retailguy]

Read Mike Busch's article in EAA magazine (about 4 or 5 months ago) regarding oil. It's either burned, pumped overboard or leaked into engine compartment.

He discusses each in detail.

I read this a couple days ago. Didn't really put 2 & 2 together until I re read it this morning. I'll look again tonight, but I'm now thinking oil is exiting through the breather tube rather than the exhaust pipes. I don't remember much oily substance on the exhaust pipes.

 

[retailguy]

Check the breather tube,and the wet pump. My 59 Travelair had very low oil consumption ,did have to change out one of the pumps.

Why would the pump cause this? How would the oil exit the engine? Through the breather tube?

 

[Clark1961]

I read this a couple days ago. Didn't really put 2 & 2 together until I re read it this morning. I'll look again tonight, but I'm now thinking oil is exiting through the breather tube rather than the exhaust pipes. I don't remember much oily substance on the exhaust pipes.

Check engine blow-by by hooking an airspeed indicator to the breather tube. Sounds weird by that is one way to do it. Any indication of 90 knots or higher says that there is too much blow-by.

The blow-by will overwhelm the air-oil sep and you end up with a mess.

If air-oil sep has insufficient material or if the material is fouled (needs cleaned) then it won't function and oil will go overboard. If oil return line from air-oil sep is plugged then oil will go overboard.

When I had an oil consumption problem we checked all aspects of the air-oil separator since it was the newest item then my A&P stumbled across the airspeed indicator check of blow-by. I ordered new cylinders shortly there after and the oil consumption problem was solved.

 

[Henning]

Is there anyway I can test this other than just having the seal replaced? Reason behind asking, is there is no clear cylinder that is causing problems, yet it has symptoms of having excessive pressures. There is lots of oil under the left wing which may indicate oil leaving the engine through the breather tube.

Would this seal increase crankcase pressure?

That's exactly what it does, it takes air in through that seal and it blows out the vent. I had to deal with the same thing on the 310.

 

[JHW]

Why would the pump cause this? How would the oil exit the engine? Through the breather tube?

yes, the outlet from the wet vacuum pump is usually tee'd into the breather tube. There may or may not be an oil separator in between.

 

[Henning]

yes, the outlet from the wet vacuum pump is usually tee'd into the breather tube. There may or may not be an oil separator in between.

I have yet to see a wet pump instal that didn't have a separator, but I guess you could. Either way though, a separator can get overwhelmed.

 

[JHW]

I have yet to see a wet pump instal that didn't have a separator, but I guess you could. Either way though, a separator can get overwhelmed.

They were almost certainly a later addition on your travel air as they were on mine. None of the early ones had them from the factory.

 

[Henning]

They were almost certainly a later addition on your travel air as they were on mine. None of the early ones had them from the factory.

True, but most people who add a wet pump add an Airwolf air-oil separator downstream from the pump into the breather to drain oil back to the sump. Even with them though, my bad nose seals caused them to be overwhelmed.