Loctite 515 Only - Case Halves

[Grant]

Planning to start assembly of my engine next week. It sounds like the current guidance from Lycoming is to use only Loctite 515 on the case halves and NOT to use silk thread. Anyone been brave enough to omit the silk? I used 515 and silk on the last one and its dry as a bone.

Thoughts

[J5Ron]

I omitted the silk and have one small leak…I would use the silk if I do another engine…

[RaisedByWolves]

I have heard it works good with the lycon o ring


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[stewartb]

My 2019 factory new IO-390 has thread.

[redfin]

0-360, no thread, 600hrs + no leaks ….. if I did again, maybe I would use thread?

[skywagon8a]

Use the thread. It doesn't weigh anything and the cost is nothing. Unless you want to take a chance that it won't leak?

[hotrod180]

.....I used 515 and silk on the last one and its dry as a bone.

Why do it differently this time?
"If it ain't broke, don't fix it".

[Grant]

Why do it differently this time?
"If it ain't broke, don't fix it".

I know - It's just that the current guidance is to omit the silk thread. I'm not sure I'm brave enough to use just the 515. Seems to me like it SHOULD work just fine without it but I KNOW it works just fine with it too!

Thanks Fellas!

[redfin]

I guess it’s just following the manufacturers guidelines.
I don’t think anyone is trying to ‘do it differently’, other than Lycoming changing their advice.

[stewartb]

When was this advice published?

[Steve Pierce]

What I read from Lycoming was that it was optional, silk thread and Aviation Permatex or Loctite 515. Have done both recently and in the past without issues on any.

[Steve Pierce]

My 2019 factory new IO-390 has thread.

How can you tell?

[stewartb]

I changed the sump. It was obvious.

[Steve Pierce]

I changed the sump. It was obvious.

Yep, you can see the thread at the sump. Didn't know if they documented it on a work order or something. It was a Thunderbolt engine?

[stewartb]

Yes, Thunderbolt. I trimmed thread at the front of the case. Lycoming had placed their sump gasket over it.