231 - AOG - Oil out the breather

[vance.k]

Hello MSers;

Flying from Denver to ABQ, just SE of Alamosa, burning smell in the cockpit.  Immediate diversion to Alamosa.  Puddle and oil all over the belly, coming from the breather.  Also, the tube in front of the oil/air separator was off.  I’m 1Q low from where I started in Denver.  Did not notice anything amiss with the engine, normal temps, good oil pressure, power normal, etc.

Mechanic is driving up tomorrow to take a look, but wanted to get advice from the group.

My question is mostly, the hose that came off the separator, is that a cause or effect?  Did it get blown off due to the crank being pressurized, or did it somehow fall off and cause the separator to not work correctly and start dumping oil?

I’m assuming I lost a ring, but we’ll investigate tomorrow.

Thanks for your help;
Vance

[exM20K]

My guess would be that it fell off and you have no piston problems, but I'd want to know for sure.  Compression test is useless.  The shop should have or be able to borrow an oil cap fitted with an airspeed indicator.  Refill the oil and run it up with this cap in place. It's the best way to know for sure if you've got a pressurized crankcase problem.. there's a CMI S/B that talks to this diagnosis. Your a&p should be familiar. 

 

Good lick

[Jim F]

Hi Vance,

The hose that's off is the crankcase breather. Good news if you were blowing oil out of the breather the rear baffel would be soaked.  The belly oil is not much oil. One quart of oil on the belly will look like the engine came apart.  I would look for a oil leak just above the left cowl flap. Your mechanic will pop the cowls and find the problem.  The smell was probubly the blow by out of the breather. The 231 firewall is not really sealed very well so most likely that is what you smelled. 

Jim

[jackn]

My guess, the breather tube disconnected from the air/oil separator, then ram air blew into the a/o separator blowing all residual oil out. I don’t think you have a problem. 

[vance.k]

Great feedback guys, thank you!  I am starting to think along the same lines, that high pressure / ram air on top into the a/o could be the causal issue once the top breather hose fell off.

I’m not 100%, but am extremely confident the oil on the belly is coming from the breather sticking out the bottom of the cowl flap.  Inside the bottom cowl is clean and there was a good amount of oil dripping out of the tube end after shut down.  The photos were not definitive, sorry, but I spent a good amount of time looking inside the cowl and it is clean in there.

Thanks again!
Vance

[takair]

I tend to agree with the above.  However, I wonder if your separator has some plugged up or froze up causing the line to blow off?  What type of separator do you have?  Would check to be sure air flows through it.  Does your breather line have a “whistle slot” to prevent it from freezing up?  Strange scenario given the the clamp is still on the line.  Maybe it was just not secured over the line correctly.

[vance.k]

Hi everyone,

Just wanted to follow up with the resolution. Went to the plane today with my mechanic and IA armed with the ideas above. Upon closer inspection, it was pretty clear that the breather hose was probably not well secured onto the o/a separator. The hose was extremely hard and the bulge for the barb was outside the clamp, and it was too short. Kind of seems like it was just butted up against the o/a and somehow finally became dislodged. I picked up the plane the very end of May and have flown about 140 hours before this happened. Hard to say why this time.  We hadn't messed with the breather at any point.

To answer some of the questions, no icing and there is an ice/whistle hole on the pipe pretty high up inside the cowl. 

We replaced the hose, cleaned it up and did a test flight, all good. Flew it home to abq without incident. 

Thanks again for the incredible support and ideas. 

Vance

[carusoam]

Vance,

Good to hear all is well....

If a ring is an issue, with increased Case pressure...  you will probably see a corresponding color change with the oil.  Dark, on the way to black.  The oil will begin to smell like exhaust too...  lots of bubbles/foam in the oil? That kind of thing...

PP ideas only, not a mechanic.

Best regards,

-a-

[N231BN]

Just an FYI, I don't have a separator on my breather line and I don't have anywhere near as much oil on my belly. Your separator may be hiding another issue.

[KSMooniac]

The breather tube is located there by Mooney. The exit hard line is located via a screw and hole that goes through a clamp that is mounted on the firewall, so there isn't any way to adjust the position.

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