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Oil leak finally found but what can I do?

jdeas

Well Known Member
After chasing this problem for a few months I sealed the bottom of my rear baffle and can now see that I have an oil leak not in the accessory case but where the case bolts together top rear.
Glad to have finally found it but now I'm not sure if anything can be done short of splitting the case :(
When I found this I removed to last three case bolts and torqued them to ~110 inch/lbs and cleaned all the surfaces.
I know the torque is over the value from the rebuild manual but it seems that most mechanics are tightening these up to just over 100 inch/lbs in the post I have seen.

Here it is after an hour flight.. No discernible difference in the leak.






Is there anything else I can try? The leak is large enough to be a real issue.
 
Try this

I'd spray a little contact cleaner or brake cleaner on the joint line.
Not too much. You don't want to wash out any sealer you have left.

Then use loctite 290 self wicking. Just put some on the case split line and let it wick in for a few minutes. Wipe off excess.

This is done with case bolts tight.

It has worked for me on more than one occasion.
Try it and let us know how it worked.

Mark





After chasing this problem for a few months I sealed the bottom of my rear baffle and can now see that I have an oil leak not in the accessory case but where the case bolts together top rear.
Glad to have finally found it but now I'm not sure if anything can be done short of splitting the case :(
When I found this I removed to last three case bolts and torqued them to ~110 inch/lbs and cleaned all the surfaces.
I know the torque is over the value from the rebuild manual but it seems that most mechanics are tightening these up to just over 100 inch/lbs in the post I have seen.

Here it is after an hour flight.. No discernible difference in the leak.


Is there anything else I can try? The leak is large enough to be a real issue.
 
Last edited:
Leak Fix

If you clean the seam with MEK, wire brush and clean again with Brakleen, then let dry and lay a bead of Scotchweld DP-190 along the seam it will stop the leak. You will also make work for whoever does the next overhaul..... good luck, Russ
 
I had a similar leak along the top of the case. Bob Japundza suggested pro seal and it has worked for 500 hours. Clean area, sand off paint at seam and then lay a fillet over the joint. Let it cure before for a few days before starting engine.
 
I had a similar leak along the top of the case. Bob Japundza suggested pro seal and it has worked for 500 hours. Clean area, sand off paint at seam and then lay a fillet over the joint. Let it cure before for a few days before starting engine.

Another vote for proseal, I used it to stop a case leak on a VW-based aviation engine.
 
First attempt was pretty good

From Mark's suggestion and the Loctite green instructions for filling voids, Preheated the engine, cleaned the case split with acetone then brake cleaner.
Applied a light bead of 290 while still warm then let sit for over a day.
I did a test flight yesterday and the leak has been reduced to maybe 10-20% of what it was. I have now re-cleaned that area and re-applied more 290 to about 1" of the gasket area.
When it's time to rebuild I might wish I had used proseal instead of 290 but I have already started down this path and it is working!
 
Case oil leak

Clean off seam with MEK, pull a vacuum on the case through the oil filler tube with a vacuum cleaner and run a bead of super glue along the seam....has worked for me in the past.
 
Vacuum would probably help any of these solutions

Clean off seam with MEK, pull a vacuum on the case through the oil filler tube with a vacuum cleaner and run a bead of super glue along the seam....has worked for me in the past.

I assume you would block or restrict the crankcase vent while doing this
 
Sealant

Plus one for proseal.
I think the revised torque for the 1/4' perimeter bolts is 96#. but I can't find the reference.
I don't like attaching baffle brackets to crankcase perimeter bolts. I run diagonal braces from the rear cylinder rocker bolts and/or use the accessory case bolts as on many Pipers, Cherokee, etc.
 
Bummer

The reason the oil is leaking at that location is because that is where the camshaft journal is supplied oil psi. The case has fretted causing the thread seal on the back bone in that area to become compromised and the oil psi is bleeding out from the camshaft saddle. This is a regular problem I see in high time Lyc engines. I see a bunch of good ideas here concerning putting a band-aid on the problem but your first inclination is correct. The correct way to fix the problem involves splitting the case and further more it?s a good sign of more problems to come down the road. (thru bolt leakage, and main bearings shifting) feel free to give me a call if you want to talk about it. 863-655-5000 Jimmy. P.S. check Lycoming SI342 on you injection line clamps. 
 
The reason the oil is leaking at that location is because that is where the camshaft journal is supplied oil psi. The case has fretted causing the thread seal on the back bone in that area to become compromised and the oil psi is bleeding out from the camshaft saddle. This is a regular problem I see in high time Lyc engines. I see a bunch of good ideas here concerning putting a band-aid on the problem but your first inclination is correct. The correct way to fix the problem involves splitting the case and further more it?s a good sign of more problems to come down the road. (thru bolt leakage, and main bearings shifting) feel free to give me a call if you want to talk about it. 863-655-5000 Jimmy. P.S. check Lycoming SI342 on you injection line clamps. 

Thank you.
 
Looking better

Jimmy, I am worried about fretting. Another data point for this engine. The engine was torn down to install a new cam then sat pickled on a shelf for more than seven years. From conversations with others, all the seals are most likely dried out and prone to leak. I did replace the sump and front seal.

It may come down to to splitting the case but the option of using a ridged filler (Loctite 290) over proseal was to address how fretting may continue with a soft surface treatment where a solid penetrating sealer would help combat it.

Last test flight was 1.5hr and the leak is pretty much gone.:)


I plan to keep an eye on the seam and if it opens back up I'll re-evaluate the situation to split the case. The engine is old but the hrs are lower than expected. Under 1700 TT and only 150 SMOH

As for the fuel lines, there is another clamp just out of the picture. The engine was in a Piper and the lines are as supplied. Reading the document, I appear to be within compliance as to supported lengths, clamps, etc.

Thanks to all for the suggestions!
 
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