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Mystery oil leak

coxcub

coxcub

PATRON
Devon, England
I have an oil leak (O320 A2B) which shows itself by droplets being deposited on the inside rear of the left cowling about half way up. I am aware of a small leak from the vacuum pump adapter and thought it might have been picked up from there by the cowling airflow and deposited on the left cowling.
However I carefully shielded that (the known leak) and did another ground run - still the cowling gets sprayed.
I also put a temporary extension on the breather pipe to outside the cowling as I thought it might have come from there - assisted by some strange airflow. - no change.
The engine and acsessories are otherwise clean.
Has anyone seen this before or have any ideas 'Whence this oil came'
Many thanks

Frank
PA18-150 G-DADG
(I'd post a picture if I could work out how to do it)
 
leak

Rocker cover gasket or maybe a drain-back tube with a loose hose clamp. do you have the new style rubber gaskets on the rocker boxes?
dave
 
oil cooler back there?

pressure leak can come/spray from far away..... keep shielding by spots and work shield to source....
 
I also have the same problem, same engine, O320A2B 150 hp narrow deck. Just came thru annual so we looked really hard thinking maybe nose seal (oil up front, too) but that was not the culprit. Replaced the crush washer back where the oil temp bulb goes into the engine block. All that did was change the oil "spray pattern" a little.

Push rod tubes seem to be sealed ok and no seeps apparent around the rocker covers. Engine doesn't seem to be using oil, and I don't have to add a quart (getting somewhere around 10-12 hrs/qt) very often, but just don't like the mess.

This is a real headscratcher.

Bob
 
If your engine is clean (apart from said leak), and you suspect possibly the nose seal/push rods/oil cooler/oil filter adapter (etc), a bit of tyre talc will say wonders about the suspected source.
 
bobnall said:
I also have the same......... Replaced the crush washer back where the oil temp bulb goes into the engine block. All that did was change the oil "spray pattern" a little.
.................
Bob
Click to expand...

is the bulb screwed into the proper adapter? there are 2 different types out there...
 
Mike....thanks for that tip. I did not know there were 2 different types of adapters. I've just used the one that was on the engine when I bought the airplane. I'll look into that.

Robl...yes the engine is very clean. In the process now of flying, then looking, then flying some more and looking to see if I can see where oil is coming from. So far, no joy, but the process of really looking is just now starting. But thanks for the thought.

Bob
 
Bob, a friend of mine here had an oil leak on his Cub that could not be pinpointed, no matter what he did. This went on for a number of weeks. It would show up on the prop as a spray pattern, but the prop seal itself was clean. WHERE is this stuff coming from??? How is it blowing back out the cowl and hitting the prop???? :-?

Finally Andy looked at it, rubbed some on his fingers, smelled it and said, "that doesn't smell like engine oil." Whereupon everyone looked straight up, directly at the oil droplets forming on the bottom of the hangar door winch case... :D Since he always parked the airplane in the same spot...problem solved! Move it back a couple inches and call airport maintenance.
 
The best way I have found to find an oil leak is to take rubbing alcohol and chalk line chalk. Mix up a small amount and after cleaning suspect area paint mixture on with small brush. Let dry then do run up and mystery solved.
 
I use a dye penetrant developer which is white and in a spray can. It is normally used when looking for cracks in parts. I just clean the suspect joint, then spray on the white powder which is suspended in a liquid, let it dry, run the engine for a short time, and look for a change in the white color where the oil seeps into the white powder.
 
Had the same issue with my O-235 in the same spot except on the right side. Never could find the source. Even rebuilt one of the oil return lines because the flange appeared to be work hardened out of existence. Still no change and the oil was there at every preflight. Then one day it wasn't -- it just stopped. Apparently whatever it was sorted itself out. Haven't see anything inside the cowl since.
 
oldbaldguy said:
the oil was there at every preflight. Then one day it wasn't -- it just stopped.
Click to expand...

The gremlin moved to Devon, England.
 
I have found oil leaking into the muffler heat shroud and it gets blown out the end on to the side cowl doors.

Jason
 
Seems like mags are always a tough spot to really dry up too.. That oil ends up just about where you describe.
 
bobnall said:
Mike....thanks for that tip. I did not know there were 2 different types of adapters. I've just used the one that was on the engine when I bought the airplane. I'll look into that.
Bob
Click to expand...

just thinking........

might try temporarily wrapping/covering that joint with tin foil, see if spray on door disappears and tinfoil get oily inside......

the bulb/solder on it can get quite deformed over time and not seal well, and your comment about changing spray pattern makes me think.........
 
Thanks every body for some great ideas/solutions.
The only place I have a leak in an otherwise dry engine is from the accessory drive for the vacuum pump.
I think what is happening is - drive leaks, drips onto heater shroud as suggested by Jason and then blows onto cowling.

Am presently wrestling with the old seal in the adapter just can't get it to budge - possibly need to get a bigger hammer!! I'll come back to it in the morning - it'll probably be easier then - these sort of problems usually are after a good night's kip.

I'll let y'all know if its solved the problem when it's all back together.

Frank
PA18-150 G-DADG
 
Take an old T shirt and rip it into 1" strips about a foot long, after you clean the engine, take the cotton strips and tie them to everything that you think might be leaking, pushrod tubes, mag base, etc, make sure there not touching anything hot like exhaust manifold, go up for a 10 min flight and see what gets dirty, works great.

Glenn
 
Pushrod tubes will leak at the heads and drip down between the fins and blow on the cowl doors. makes it look like a rocker cover is leaking.
 
I thought someone would have come up with this by now... they haven't
So here I goes.....

STOP USING MYSTERY OIL .... (ie: mmo)

Sorry I couldn't help myself

ha ha ha ha
 
I found it folks!
Having changed the vacuum pump adapter oil seal - no more mess there but oil still showing on the cowling. Some serious searching then took place with mirrors and and various body contortions to have a good look at the difficult to see places. Nothing immediately obvious except left rear oil drain back rubber link pipe appeared damp. Many more contortions with screw drivers found both clamps were slack
Clamps tightened (with difficulty!) - problem solved.
However it's interesting that the oil was making it's way from there to the cowling without touching anything else on the way - there's some strange airflow around there!
 
It's interesting that there's a recurrent AD on those drain-back tubes, but there's no requirement to check the rubber hose connexions!

A small lesson learned for us all.
 
Yesterday I found a possible source of my oil leak. The quick drain is oil wet around the threads and I wiped off excess oil from that area. It's on tight, so maybe it needs to be replaced. I plan on changing oil after I return from JC, so will look at it then.

Are quick drains repairable or should they just be replaced? I've never priced them, so does anyone know about how much they are?

Bob
 
My quick drain was always damp and shiny as well. We pulled it out during recently and my mechanic replaced the o-rings and now it's as good as new. They had the o-rings in stock, so apparently they can be rebuilt. And I don't think it cost $80 to rebuild it.
 
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