Chasing oil leaks

[Sonex1517]

At the request of member Doug Raby, I am posting this for others to use as a reference. This is not intended to be technical support for AeroVee oil leaks, nor is it endorsed by Sonex Aircraft LLC or the Sonex Builders and Pilots Foundation as official advice. It is Doug's solutions shared with the Sonex community

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Right from the first run of my engine I had several oil leak issues to deal with. So, I'll try to give you the complete picture( as much as I can recall at this point) of the various things I did to seal up the engine.
Here are the areas that required attention on my engine:
- the oil pump
- pushrod tubes
- oil slinger
- valve covers
- rear main seal

Let me say that I got excellent help and advice from many expert builders during my testing. And, I had their high standards by which to measure my own progress. Both Robert Eley and Peter Van Schalkwyk, figured heavily in working through the problems. I know you know their planes and the quality of their work.

Let's deal with this issue first.

Credit is due for Steve Bennett via Peter for this.

This is a standard automotive oil seal. Ironically the ID is 2180 thousands.
Before I installed this there was a persistent seepage getting past the slinger and the auger built into the prop hub. I finally realized that I had too much clearance between the hub and one side of the case. The result was the auger was doing nothing.
Here's how it works. The engine is already built so there's no way to get a seal at this end of the engine. So what you do is cut right through the rubber and steel ring on one side of the seal and only cut the steel 180 degrees around the seal.
Then you can twist the seal and get it over the hub.

I polished the hub with some Scotchbrite to make a smooth bearing surface for the seal.

I pushed the seal up against the engine case and used a zip tie to gently squeeze the open ends of the seal back together.

Then I sealed up the whole thing against he engine with rtv. Next, I installed that nifty bracket that snugs the whole thing in place. The rtv bonds the seal to the case as well as the bracket, keeping the seal from spinning. I think I oriented the seal with the open end at nine o'clock so the bottom of the hub had 'good rubber' on it.

Make sure to lube the hub with a light coat of grease prior to seal installation so the seal doesn't burn up.

Initially I saw a bit of black residue as the seal got seated , but that was temporary.
This solved my oil leak at the slinger.

http://api.zenfolio.com/cdn/pub/cshedmfrurkc/0/null/mh/g8ol6-5iavbygcdcem6a/s6/v143/p576236548-5.jpg?sn=2YH&tk=07uFRDq5OVpYaeEXaMj940J3am7j-aHTplXt9KtX5lY=


Robbie Culver
Sonex 1517
Chicagoland
Tails and Wings complete - finishing fuselage.
N1517S reserved

[Sonex1517]

More to share from Doug

Before I get into the second instalment, I should qualify my findings and solutions as my own and as the saying goes 'your mileage may vary'.

Back to that external seal...I had discussed the problem with both Kerry and Jeremy and they both had good suggestions for other possible solutions, all of which I pursued. So, in no way am I critical of their support. I will say, that it put a smile on my face when the cowl came off the Sonex factory plane at ASA 2013 and there was what looked like an external oil seal.

Now for a look at the oil pump...

Credit here goes to the two Roberts; Eley and Frost. This is a very touchy one, since close tolerance here is so critical to oil pressure. I don't think there are gaskets for the pump or cover in the plans - just anaerobic sealant. IMHO that's the way to go if you can do it without leaking. That way you'll get the best oil pressure.

I managed to seal my pump buy using a very, very thin gasket which I cut out of a manilla file folder and applying a thin coat of the sealant. The other thing that helped was coating the bolts with anaerobic sealant. This helps to discourage oil from following the threads out.

Push rod tubes...

This was a biggie for me and a real bugger to solve. The problem here ended up being a tiny crack in the weld in the bellows of one push rod tube.

I knew there was a leak in that vicinity of the engine but isolating it was difficult because of course the wind from the propeller sprays the oil everywhere. I had my suspicions about the location of the leak and finally found it by taking a short flight with a blue shop cloth wrapped around the tube. Et voila, another step forward. I replace all the stock pushrod tubes with stainless steel 'windage' tubes and silicone gaskets.

Needless to say by the time I got this fix done I was pretty good at pulling and reinstalling the heads.

More to come...

Doug
Sonex C-GGDR

[Sonex1517]

As I was working my way through all these oil leaks I had encouragement from all kinds of people. One of the recurring themes was "it's an airplane, if it's not leaking oil it must be out of oil". I understand that, but I just wasn't happy that my shiny new plane was getting all that unwanted rust proofing. Besides that I didn't want to worry that a little leak would turn into a big leak at 3000 feet. I wanted to have a plane that I trusted so I could make the trip to Crossville and back And so I continued my quest for a dry belly.

Having the valve covers on and off and on, is a way of life with the VW. If not for pushrod problems you will at least be removing them a half dozen times in the first year for valve adjustments. I use cork gaskets with a light coat of aviation gasket sealant. It's that brown stinky stuff - Permatex #3.

I even put a bit on the little gaskets under the valve cover bolts. It's always advisable to have a fresh set of valve cover gaskets on hand, because that sealant is sticky, making the removal of the valve covers a bit tricky, and prone to damaging a gasket.

Rear main seal...

The final area that oil was leaking was from the rear main seal. It took me a couple of tries to get this one solved. One seal got pinched and had a tiny fissure which caused a leak, then I didn't pre-lubricate the seal which burnt out the seal during the initial run in. From what I learned I was able to get the current seal installed successfully.

I got pretty good at removing and reinstalling the engine on the plane but at the end of all this, I finally had a plane that didn't leak oil.

I could hardly believe it myself that the plane made it to Crossville, TN and back to Peterborough, ON without leaking a drop.

If your engine leaks a bit it's probably not life-threatening. And who knows mine might spring a leak sometime in the future. What I can say for sure is that I sure know a lot more about my little plane as a result of tracking all these problems down.

I will always remember Kerry saying, on one of our many discussions, "You'll have to find out where the leak is and fix it". I also remember thinking at the time that that wasn't very helpful. And to be truthful, feeling a bit pissed off. I now realize how sage that advice was. Being pointed in the right direction often comes in subtle ways. We are, after all, building these birds with the responsibility of success firmly resting on our own shoulders.
Feel free to email me if you have comments or questions about any of this.
Deltaromeo@sympatico.ca

[daleandee]

Hello Doug,

Congratulations on attaining a leak free Aerovee! :)

Here is a few of suggestions that I use on my Corvair that may help.

When I put gaskets on valve covers I like to use cork. I was taught long ago to never glue a gasket to both surfaces. They should be glued to the part and not the engine as the engine side will be the hotter side and more likely to "cook" the gasket and sealer making removal later more difficult. For valve covers I glue the gasket to the cover with Permatex 98H:



and use a light coat of grease on the side that will go against the block. Some use silicone sealer but I don't care for that in this area. If using silicone please use it sparingly! Keep in mind that the block side will have the better surface (truer) to seal against. That is why I only use a light coat of grease (some use motor oil) on that side.

Do not over torque! Over tightening is one of the best ways to destroy a cork gasket. When removing the cover later a light tap with a rubber mallet is generally all that is needed and many times the same gasket can be reused. Having said that ... cork gaskets are cheap and even cheaper if bought in bulk.

On the push rod tubes I noted that you used silicone o-rings. On Corvairs we have been using Viton seals on the pushrod tubes (and the oil cooler seals as well) and this has eliminated the oil leak concerns. Viton will withstand much higher temps than rubber or silicone and is more resistant to chemicals.

Lastly, on Corvair engines it is recommended to paint the pushrod tubes white (VHT paint) and this helps to alleviate heat on the tubes. Less heat means less stress on the seals.

Thanks for being honest with your frustrations in following this through. In the end you achieved the goal you were seeking and you are here to share that information with other builders. A tip of the hat to you sir!

Dale
N319WF
80.2 hours