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Oil on lower cowling

747driver

Registered User
Germany
Every time I fly I have some oil on the lower cowling around and mainly just behind the air filter. I couldn´t locate the spot where it comes from as the air stream inside the cowling is probably kind of disturbed. Only thing I can tell is the lower carb is always wet with the oil. It is a C-90-14F and I was told by other SuperCub pilots that this is normal. Don´t want to believe this however and asking for someone else´s experience.
 
It Is normal.....you can put a baby bottle on the end of your breather, or buy an oil/separator gizmo.....but I usually just wipe it off with a rag after each flight. It really is normal....I've never had one that didn't leak.
 
Wash with mineral spirits. Fly for 1/2 hour. Lots of talcum powder on whole engine. Leaks will be obvious and engine will smell great:)

Yeah....it is normal for them to leak. Its inexpensive corrosion protection ;)
 
Little Continentals are notorious for leaking push rod tubes but if your carb is wet look at the vacuum pump block off plate on the bottom of the engine ahead of the carb. When we put Tal's engine back together the carb was soaked and it was coming off this plate. Mark E nailed it when he noticed that the cover was warped.
 
I'm convinced most C-90s spend their life finding creative ways to leak. :wink:

I had a lot of fun chasing down the leaks after overhaul. The bulk were push rod tube leaks. I had a warped vacuum pump plate that dumped some oil on the carb, so I replaced that and voila problem solved. :smile:

This was nowhere as insidious and maddening as the slight leak before overhaul that was due to a minisuclue crack in the crank that enjoyed making a very fine spray of oil all over the front end once the oil warmed up. We all thought it was the prop seal! Nope. Sure feels good flying behind that nice, new crank. ;-)
 
I think I go the way behindpropellers described, until now it is almost impossible to locate the leak. But it is not the breather tube, the tube is wetting the lower fuselage more to the rear.
 
Ditto the warped vacuum pump plate. It took ages to find it, I thought the left rear stud had cracked and the oil was escaping via its threads until a sharp eyed buddy saw the first drip on a dedicated ground run with the bottom cowl removed. The plate blocks off an oil feed intended for the vacuum pump bearings from the camshaft front bearing gallery and this is located midway between the studs on the left hand side of the crankcase and there is a lot of pressure behind that, grollying up the nuts just tends to warp the plate more, the best bet is a thicker stiffer replacement plate with a decent fresh gasket. But could I find a part number for the plate? not in any parts listing I have seen, only the vacuum pump.

I think the other source of leaks under the engine are inlet valve guides that drip oil into the Carb heater box

UKCN
 
I think I got one of these plates from El Reno Aviation in Oklahoma. They know the little Continentals well.

Mark
 
Instead of looking for a new plate, why not just clean up the old one on a surface plate with some fine sandpaper?
 
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