O320-150 oil leak

[Larry Huntley]

I have a friend w/ an O-320- 150 case that seems to be leaking through the seam at top of the case . Yeah, I know, Tear it down and clean and reseal. Trying to avoid that. Leak is not really very bad, but it does send oil to his windshield. Anyone have a material to use or method that might seal this w/ out teardown? Your help will be gratefully appreciated. Larry

[Gilbert Pierce]

If it is leaking around the bolt, remove it and clean the hole and then coat the hole and bolt with #2 Aviation Permatex. That worked for me.
If it is the seam between the case half’s I don’t have a solution. Blowing oil on the windshield indicates he may have a pressurized crank case aggravating the problem. In my experience a seam leak just seeps.
Ive had a prop seal leak that looked like a crankcase seam leak as the oil flowed down the seam from the prop wash and cooling air.

[dgapilot]

Most
Leaks on the case halves are either from improper assembly, or fretting of the case halves. Using the incorrect sealant, too much sealant, improper torque, and a bunch of other things fall into improper assembly. Any fix you try and apply will just be a band aid fix and won’t last long term. I have to agree with Gilbert on the pressurized case issue. Most leaks will make a mess, but don’t get up on the windshield. A pressurized case will make any leak exponentially worse. Suggest you troubleshoot that. There are other threads here that talk about using an airspeed indicator to measure case pressure. A quick check can be done by pulling your valve covers. In every case I’ve seen with high case pressure, the exhaust valve guides were shot. Compression was fine, but when running exhaust would get through the guides and pressurize the case through the upper end drains. When you pull the covers, if the guides are leaking, you will see the light brown/tan lead bromide (assuming you are running a gas).


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[Larry Huntley]

If it is leaking around the bolt, remove it and clean the hole and then coat the hole and bolt with #2 Aviation Permatex. That worked for me.
If it is the seam between the case half’s I don’t have a solution. Blowing oil on the windshield indicates he may have a pressurized crank case aggravating the problem. In my experience a seam leak just seeps.
Ive had a prop seal leak that looked like a crankcase seam leak as the oil flowed down the seam from the prop wash and cooling air.

Thank you Gilbert and dgapilot. He is back North and I am in Florida, but I try to do best I can long distance. We will try sealing the bolts, and he had the shaft seal replaced last summer but I am afraid it is the seam on top that is leaking. Can't understand how the engine can build pressure and leak when it has the breather to relieve pressure. Your thoughts? Will check on the airspeed indicator idea. A Band-Aid approach here would be somewhat acceptable as he is losing almost no oil, so it doesn't seem to be a danger, just an annoyance. BTW, he is using autogas so don't know if there would be any evidence. Compression checks good. Larry

[Gilbert Pierce]

We had a fuel injected EAB make an off airport landing here twice The third time destroyed the aircraft.
The problem was a Mud Wasp (mud dobber) nest blocking the crankcase vent.

[Larry Huntley]

Wow! Expensive bug. Will check that for sure. Get plenty of them in NY but never thought of them going up the breather tube. Thanx, Larry

[JPerkins]

I have had luck with Seal-All on leaking case seams. Not a permanent repair but a long term one at least.


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[Larry Huntley]

I have had luck with Seal-All on leaking case seams. Not a permanent repair but a long term one at least.


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I wondered about Seal-All. Good to hear from someone who has had experience using it for this purpose. Thanx, Larry

[Steve Pierce]

Some friends attended Lycoming school and told me about a method taught there where they applied a vacuum to the engine and used green Locktite to the crankcase halves. You have to clean all the oil out of the leaking area.

[dgapilot]

Some friends attended Lycoming school and told me about a method taught there where they applied a vacuum to the engine and used green Locktite to the crankcase halves. You have to clean all the oil out of the leaking area.

I’ve used the vacuum and green lock tote on Mooney fuel tanks, never tried it on an engine!


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