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Oil in the induction system.. Ideas?!

S

SegevFly

I'm New Here
Hi Guys,

Calling on engine people!

We found 3 of 4 cylinders were wet around the inlet valve guide in an IO360 after pouring a not-insignificant amount of oil out of the main engine intake tube (before it branches off to individual cylinders).

Pulled all 4 jugs off and sent them to the a local engine shop.

They all come back with pretty paint, 4 new pistons, few new valves springs, new exhaust valve, new rings and a big $$$ bill. They say we did not replace any of the intake guides as they'd already been done once, can't do again and they looked fine and within the Lycoming tolerance.

We put all the jugs back on. We go flying. 2 hours later, check intake and it's got a puddle of oil in it again.

The engine shop claims it cannot be the inlet valve guides leaking as any oil would be sucked into the cylinder and burnt. There is no way it can be in the intake.

We are now 11 hours after the engine overhaul, been running high power settings for a long period to brake-in the engine per their recommendation, with no sign of improvement.

Interestingly enough, we only lost 0.5qt of oil in these 11 hours..


Attached pictures of the ground below the aircraft, as well as the intake tube

https://ibb.co/ryN7Hyb


https://ibb.co/2tCNmkf

https://ibb.co/dKm3k3N

https://ibb.co/zNZZZss

https://ibb.co/7pY5jZ8

https://ibb.co/2vFYR2q


Open to suggestings and ideas



Many thanks,
 
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SegevFly said:
The engine shop claims it cannot be the inlet valve guides leaking as any oil would be sucked into the cylinder and burnt. There is no way it can be in the intake.
Click to expand...

I'm not sure if this is true.... I'm thinking that there will be oil in the valve covers that can seep past the valve guide after shut down and into the intake. In any case, if it's not causing a problem with power, I'd recommend placing trays under the leaks and keep flying until you're ready to overhaul the engine.
 
Is the main oil seal on the crank leaking, with the oil finding its way into the induction system through the air filter/throttle body?

Your photos don't include anything about the general condition of the engine installation, so I'm just speculating...
 
A friend of mine had oil pooling in the same place and it turned out to be a tiny crack in the sump letting oil in the sump migrate into the intake area. Just FYI
 
I do not understand how it is getting on the ground if the oil is in the intake tube. Is it coming out of the throttle body?
 
kkmarshall said:
A friend of mine had oil pooling in the same place and it turned out to be a tiny crack in the sump letting oil in the sump migrate into the intake area. Just FYI
Click to expand...

+1

That fits what you?re reporting especially if the engine has a sniffle valve and the oil on the floor is right beneath it. Also, you?d see less oil loss at the high power settings you?ve been running where the pressure in the sump and the intake are similar.
 
Hi All,

Firstly - thank you for your time looking into my engine issues.

The engine is installed in a Pitts S1S and is a vertical intake. Therefore no sniffer valve, nevertheless, the oil just simply run out of the throttle body, then into the floor via a small drain hole which is located in our air intake.

Based on the comments and suggestions provided, I am going to try and locate another sump, install it on our aircraft and fly to identify if it is the issue, if it does, I will get a new one from Superior or Lycoming

While perhaps costly, I am unable to determine what the oil is coming from otherwise..


I attached some additional pictures for your information, and I promise to let you know how I go!

https://ibb.co/syt2KgJ

https://ibb.co/mHH9Vkz

https://ibb.co/CQ8JjHs

https://ibb.co/nwQ9Xqy

https://ibb.co/hBvxC0c

https://ibb.co/jwgmRH1


Thank you again,
 
At idle and low power the intake has a vacuum, the rocker box has a good bit of oil in it. Since the intake guides end opposite the end in the rocker box is in a vacuum, some oil will be sucked into the intake port. Most of this oil will go into the cylinder and get burned, the rest drains into the intake system.
On horizontal induction systems there is a one way valve in the bottom of the intake plenum to let this oil and any residual percolated injector fuel drain out. It is called a sniffle valve.
 
my vote would be a crack in the sump somewhere, or a bad seal somewhere that keeps the sump separate from the intake tubes.
 
SegevFly said:
Hi All,

Firstly - thank you for your time looking into my engine issues.

The engine is installed in a Pitts S1S and is a vertical intake. Therefore no sniffer valve, nevertheless, the oil just simply run out of the throttle body, then into the floor via a small drain hole which is located in our air intake.

Based on the comments and suggestions provided, I am going to try and locate another sump, install it on our aircraft and fly to identify if it is the issue, if it does, I will get a new one from Superior or Lycoming

While perhaps costly, I am unable to determine what the oil is coming from otherwise..


I attached some additional pictures for your information, and I promise to let you know how I go!

https://ibb.co/syt2KgJ

https://ibb.co/mHH9Vkz

https://ibb.co/CQ8JjHs

https://ibb.co/nwQ9Xqy

https://ibb.co/hBvxC0c

https://ibb.co/jwgmRH1


Thank you again,
Click to expand...

I would check each drain back line from the rocker boxes. A plugged line will allow excess oil to accumulate in the rocker box and if / when the level gets up to the intake valve guide, will leak into the intake runners. Pull them quickly after a long engine run and it will be obvious if you have a plugged line. This type of problem would only creating dripping on the floor after long runs and not after short runs. You also want to pull each intake tube and check for wet oil. You want to know which cylinder (possibly multiple) is the source.

Clearly a casting crack could cause this. However, it is a tough diagnostic exercise to start with and seems less likely with a sump that has not leaked for many years. If you find a wet intake tube, you can eliminate the sump as the culprit, so would start there.

Larry
 
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Hi Guys,

Firstly - I would like to thank you all for your input and ideas with our issue - this community is awesome!


I am absolutely excited to update you that the issue was found - it was the oil sump!

While no cracks were found, the material (sand casting by Lycoming) was simple porose and allow oil to get into the air induction! Perhaps not a surprise when you think about the fact this engine part is 47 years old!

I ended up purchase a new oil sump from Superior and been flying ever since with no issue or oil in the system. Only the clear fuel it always should have.


I hope this will help someone one day.


Thanks again and happy flying,
Ido
 
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