Air/Oil Separator for the 252s

[shawnd]

There should be two beyond the metallic one from the oil separator. One from the front of the engine for overflow of fuel. If you run low boost with mixture in, you will see fuel come out of it. There should be another one from the turbo waste gate controller I believe.

 

[Ragsf15e]

6 minutes ago, shawnd said:

There should be two beyond the metallic one from the oil separator. One from the front of the engine for overflow of fuel. If you run low boost with mixture in, you will see fuel come out of it. There should be another one from the turbo waste gate controller I believe.

 

Yeah, there's several drains down there for sure.  I'm slowly tracing them all.  I was just surprised that both air oil separator drains went down there.

[shawnd]

Wait, I misread your previous post. I have one on the side but looks like it's going back in and not down? Could be wrong, haven't looked at the connections in a while. 

 

[shawnd]

Or is that an air inlet from intake side?

[Ragsf15e]

4 hours ago, shawnd said:

Wait, I misread your previous post. I have one on the side but looks like it's going back in and not down? Could be wrong, haven't looked at the connections in a while. 

 

That little one on the inside of mine goes down and empties underneath right next to the main air oil separator drain.  Where does your smaller one go?

[shawnd]

I will have to look but next time I open up the cowling - in about 5 hours of flight time. 

[Ragsf15e]

I looked very carefully at the IPC and it appears impossible to tell where the smaller line out the inside of the air oil separator is supposed to connect. My mechanic said there’s no way it’s supposed to also go down by the breather where mine is. There should be one line returning oil to the engine. Can anyone show me a picture of where the smaller inside hose off the air/oil separator connects to feed oil back into the engine?

I may also try calling around to some MSC‘s and see if someone will talk to me.

[MikeOH]

@Ragsf15e

While I have an F, not a 252, the small line out of my air/oil separator goes to a 'Y' fitting on the rocker cover drain back tubes; i.e., back to the sump.

[Ragsf15e]

Just now, MikeOH said:

@Ragsf15e

While I have an F, not a 252, the small line out of my air/oil separator goes to a 'Y' fitting on the rocker cover drain back tubes; i.e., back to the sump.

Yes, that makes sense.  My mechanic mentioned a few places it might connect (that being one).  Hopefully I can find the “stock” 252 location and make it right.

[WilliamR]

I would have thought it was in the engine IPC where the small "side" tube goes. Clearly, I'm wrong there. Going from memory on a TSIO-360-mb (and I think its the same on the -SB; have to check) the small "side" line goes to the oil fill tube which is right there on the other side of the baffle. Guess I need to reacquaint next time I go to the hangar on my -SB.  I'll try to take a break tonight and snap a pic or two.

Rags, I think we've met before. You fly for NJ, and flew F15's right?

William

[shawnd]

I agree. @WilliamR jogged my memory, I believe it goes in so that it can attach to a nipple on the oil filler tube. I should be able to take a pic this week if that’s the case. Logically it makes sense to return the oil back in. 

[Ragsf15e]

43 minutes ago, WilliamR said:

I would have thought it was in the engine IPC where the small "side" tube goes. Clearly, I'm wrong there. Going from memory on a TSIO-360-mb (and I think its the same on the -SB; have to check) the small "side" line goes to the oil fill tube which is right there on the other side of the baffle. Guess I need to reacquaint next time I go to the hangar on my -SB.  I'll try to take a break tonight and snap a pic or two.

Rags, I think we've met before. You fly for NJ, and flew F15's right?

William

William,

That might have been the person who owned my current airplane before me - Jim.  He does fly for NJ and flew Eagles.  I'm a corporate pilot (and flew F-15Es), so close!  Here's the IPC pages both for the original M20K installation and the MB and SB engines.  The AO Sep is circled although it looks slightly different in reality.  It has a large diameter breather line coming out the bottom and a smaller diameter line coming out the side.  I can't tell where the return line is supposed to connect, but you guys could be right - oil filler tube would make sense!

Drew

air oil sep.pdf

 

[WilliamR]

Here are two pics where the line comes from the separator side of the baffle. As I remembered, there is a nipple towards the bottom of the oil fill tube that the side line connects to. The nipple points outboard. Hope this helps.

See the mediocre pics. The pic of the oil separator wasn't the best since the #2 alternator was in the way so I didn't include it, but it's exactly like the one pictured in this forum, tube out the bottom and another out the side towards the bottom. 

Got it on the owner. Anything for an Eagle driver...even the family model.

Best,

William

 

[Ragsf15e]

14 hours ago, WilliamR said:

Here are two pics where the line comes from the separator side of the baffle. As I remembered, there is a nipple towards the bottom of the oil fill tube that the side line connects to. The nipple points outboard. Hope this helps.

See the mediocre pics. The pic of the oil separator wasn't the best since the #2 alternator was in the way so I didn't include it, but it's exactly like the one pictured in this forum, tube out the bottom and another out the side towards the bottom. 

Got it on the owner. Anything for an Eagle driver...even the family model.

Best,

William

 

That’s very helpful, thank you!  It also matches what I was told by another reputable source!  Now I have to wonder why mine wasn’t set up like that and what is connected to that oil filler port?!  It looks like I can take a preliminary look right through the oil filler door which is nice!  I’ll follow up soon…

[Ragsf15e]

On 3/12/2025 at 7:06 PM, WilliamR said:

Here are two pics where the line comes from the separator side of the baffle. As I remembered, there is a nipple towards the bottom of the oil fill tube that the side line connects to. The nipple points outboard. Hope this helps.

See the mediocre pics. The pic of the oil separator wasn't the best since the #2 alternator was in the way so I didn't include it, but it's exactly like the one pictured in this forum, tube out the bottom and another out the side towards the bottom. 

Got it on the owner. Anything for an Eagle driver...even the family model.

Best,

William

 

I took a picture today just to close the loop before we fix this at annual next week.  The engine has been on the airplane two years.  Installed at a reputable msc. I just got it, so no idea how long it’s been like this, however, the tube leading into the oil filler tube was not connected to the air oil separator or even capped off?!  There was a piece of blue painters tape near it. I wonder if that was on there temporarily at some time?  Fixing this should help my oily belly issue a lot!

[shawnd]

Yep, glad you found it! Sorry - wasn't able to get back to the hangar last Friday.