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Phantom Oil Leak


wlfpckrs

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Since day one after our engine mount replacement, I have had a small, aggravating oil leak that neither Sebring Aviation nor Chesapeake Aviation has been able to identify and fix. It's not using much oil, so we don't have to replace much at all, but we have a little messy cleanup after each flight. When you look at the plane from the front, if you consider the lower cowl opening to be a mouth (it looks kind of like one), we see some oil streaking out of both corners of the mouth, but more noticeable on the left (actually the right side of the plane). We also notice oil at the seam between the upper and lower cowl on the pilot side that then runs down the pilot side of the plane, just under the door. When I look at the underside of the upper cowl, I've noticed oil about a third of the way back from the front and on the pilot side. Though there is no apparent evidence to support this, I am wondering if there could be a problem with the seal between the gear box and engine. Anyone care to take a stab at this?

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I'm also looking for a small oil leak.

 

They can be aggravating, since the oil spreads out so much so quickly.

 

One trick is to clean the suspect area well, then spray it with foot powder (Desenex or equivalent)

 

This is what mine looked like:

 

5072114709_410dce6d60_z.jpg

 

You can see how even tiny areas of seepage are obvious.

 

I had suspected and replaced the oil pressure sender, but that was apparently not the issue.

 

Yesterday we gooped up the suspect bolt with some silicone and re-torqued, and after a short flight it looked better.

 

Good luck!

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Hi Guys,

 

Here are the common oil leak areas and yes they can be hard to find. Like Eddie said some type of powder like the Desenex or talcum powder will work.

Here are some common areas of leaks:

 

On the bottom of valve covers. Run your finger under them and you may find an ooze that isn't dripping,.

on the bottom of the gearbox. The gearbox needs re-sealing. Loctite 5910 or Permatex (The Right Stuff)

on the oil sending unit threads. use Loctite 567 thread sealant

the 2 fittings on top of the oil cooler. Always put a wrench on then and give them a tightening even if they feel tight.

oil filter flange.

Oil filter a little too loose.

And last, but not least, you may have drooled a little oil on the radiator during an oil change and the air rushing through spreads it around on the engine and it looks like you have a leak.

 

Always use Loctite 567 (never teflon tape) to seal your threads from leaks. This stuff is good for oils, brake fluid and fuel. It also helps lube the thread to help from galling. I use this on any threaded parts with fluid running through it. It never leaks.

 

Now what happens many times is that the high pressure air coming in through the front of the plane will blow the oil off the leaking part back to the middle of the engine or spread it around and it won't have any oil around the leak area.

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My right-side valve cover(s) ooze just a tiny bit and, if not kept clean, give me a similar oil streak down the side. We've tried everything to seal them up... new gaskets, different types of sealant/goop, and even sanding them smoother. No go - still a tiny ooze. It's amazing how far a drip will move, when blown with a 130mph wind.

Tim

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  • 1 month later...

Fuel pumps, gearbox mating surface leaks, and oil migration up cylinder studs are the 3 most common oil leaks. The oil passage going from the crankcase to the ignition housing is also a very problematic area and almost always require engine removal to address.

 

As for the picture posted above with the oil around the M8 Bolt holding the crankcase togeather, this is also another leak ive been seeing popping up on select engines. The fix for this is removing the M8 Bolts one at a time and removing the lock washer and replacing it with a An 960-516 washer. This is a factory approved modification and if you look at new production engines (2009-onwards)( the have actually done away with the M8 Allen bolts and replaced them with M8 Hex bolts with Flat washers for this very reason.

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  • 1 month later...

Update...

 

...I followed Jeremy's advice and found an AN 960-516 washer. Installed it yesterday, with the bolt smeared with blue Loctite. Did the foot powder thing.

 

Before:

 

5441771642_24b524bcbb_z.jpg

 

After 3 minutes of running:

 

5441168493_47e7a2b785_z.jpg

 

Good news: so far no leakage around the bolt head, as seen in the prior photo in this thread.

 

Bad news: seems to be some seepage from the oil pump cover and the oil fitting on the left.

 

I can just try tightening the oil fitting a bit. Is there a gasket or any special tip to stopping the seepage from the oil pump cover?

 

Thanks!

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Hi Eddie,

 

I don't know if that ooze is worth messing with unless it is getting all over the engine. You can pull the top cover and it is sealed with an "O" ring. You have two options. One clean both surfaces with a scotch pad and replace the "O" ring. If that doesn't work them apply a thin film of 5910 to the "O" ring and re-torque it.

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  • 11 months later...

I replaced the seals on #1 valve cover and fixed the my leak. I noticed (using my $69 harbor freight "Colonoscopy" scope) a little oil at the interface where the oil return tubes go into the back side of the cylinder head. The Illustrated Parts Manual shows no seals there. Are they just screwed into the head? I'm thinking it's not worth the trouble to pull the head to fix. Comments?

 

Ernie

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As an update, my problem persists. It's still just a drop or so running down the cowling after each flight.

 

I'm still suspicious about that little bit of seepage shown in my foot powder photos.

 

If I make it down to see Tad next FL trip, or out to see Roger this summer, maybe I'll investigate further.

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Hi Eddie,

 

There are many 912 owners with a tiny weep some where, but of no real consequence, but I agree it is annoying. Mine weep on two valve covers and I have tried everything to stop them and I mean everything. It doesn't hurt anything just drives me nuts.wacko.gif

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  • 2 months later...

I have a oil leak at the interface where the oil return tube goes into the back side of the cylinder head. The Illustrated Parts Manual shows no seals there - just lock tight. Are they just screwed into the head or pressed in?

 

Is there any way to address the leak without removing the cylinder head?

 

Ernie

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Hi Ernie,

Are you talking about I the push rod tubes? One of the two long tubes on the bottom of each cylinder? If so they are only held in place by Loctite. They need to be heated to remove them. Yes you need to remove the head. Make sure to oil isn't coming from somewhere else just spreading to that area.

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Hi Ernie,

Are you talking about I the push rod tubes? One of the two long tubes on the bottom of each cylinder? If so they are only held in place by Loctite. They need to be heated to remove them. Yes you need to remove the head. Make sure to oil isn't coming from somewhere else just spreading to that area.

 

Not the valve covers. Not where the oil push rod tubes go into the casing. Sure looks like the interface between the back side of the cylinder head and the tube. Are they screwed into the head or interference fit?

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Hi Ernie,

 

The push rod tubes where they insert into the bottom of the head are only held by Loctite, no threads. I haven't seen one leak there, but have seen oil from other places that get blown there by the wind coming into the cowl. I would put a wrench on the oil cooler fittings. The nut on the hose and the fitting that is in between the hose nut and the oil cooler. There is an adapter between the two that does loosen and oil oozes out and this gets blown back in the area you are talking about, but leaves the oil cooler fitting clean. I would clean everything really well and fly and look again. If you need to use the foot powder spray like Fast Eddie did to pin point the leak.

Before I pulled a head to mess with the push rod tubes I would make darn sure that is where the leak really is. The leak isn't hurting anything so take a little more time to investigate.

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Hi Ernie,

 

The push rod tubes where they insert into the bottom of the head are only held by Loctite, no threads. I haven't seen one leak there, but have seen oil from other places that get blown there by the wind coming into the cowl. I would put a wrench on the oil cooler fittings. The nut on the hose and the fitting that is in between the hose nut and the oil cooler. There is an adapter between the two that does loosen and oil oozes out and this gets blown back in the area you are talking about, but leaves the oil cooler fitting clean. I would clean everything really well and fly and look again. If you need to use the foot powder spray like Fast Eddie did to pin point the leak.

Before I pulled a head to mess with the push rod tubes I would make darn sure that is where the leak really is. The leak isn't hurting anything so take a little more time to investigate.

OK I'll check it. Thanks

 

Ernie

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If you do remove the heads and push rod covers, carefully ensure the rod covers are fully re-inserted when secured by locktite. If not fully in, yet secured by the locktite, the extra length will cause the o rings on the block to fail in fairly short order.

 

beleive me, you don't want that.

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