Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Engine case sealing
- Thread starter skidookid
- Start date
Silence....
Sounds like nobody has! I know a guy who did his a year ago with no problem, but I'd stick with the tried and true silk thread and permatex.
The problem is two fold, one you need to be quick with the case assembly or the sealant will skin over, and this is is a good time to be slow and carefull. Two, some guys will use too much and you'll have RTV squeezed out and the traveling around the oil sump.
Tim Andres
Sounds like nobody has! I know a guy who did his a year ago with no problem, but I'd stick with the tried and true silk thread and permatex.
The problem is two fold, one you need to be quick with the case assembly or the sealant will skin over, and this is is a good time to be slow and carefull. Two, some guys will use too much and you'll have RTV squeezed out and the traveling around the oil sump.
Tim Andres
A2Jake
Active Member
No
No
See this Lycoming Service Instruction
http://www.lycoming.com/Portals/0/t...rnator Crankcase Parting Surface Sealants.pdf
There is a lot of debate and plenty of discussion to be found in the archives on this subject.
We have found that Permatex 3H aviation sealer will crystalize after being subjected to heat and time. ALL of it has been removed from my shelf.
+++ Yamabond 4 has changed their formula, I No longer recommend it +++
J
No
See this Lycoming Service Instruction
http://www.lycoming.com/Portals/0/t...rnator Crankcase Parting Surface Sealants.pdf
There is a lot of debate and plenty of discussion to be found in the archives on this subject.
We have found that Permatex 3H aviation sealer will crystalize after being subjected to heat and time. ALL of it has been removed from my shelf.
+++ Yamabond 4 has changed their formula, I No longer recommend it +++
J
Last edited:
Norcalrv7
Well Known Member
Interested for you to elaborate on the yamabond. I've used it for years on Honda, Subaru, and other aluminum engine sealing needs. Have you actually tried it? good results?
Caleb
Caleb
I used an anaerobic sealant (Permatex brand) on my case with no thread. 80 hours and no leaks. I guess time will tell, but this is a common approach on sealing the aluminum case halves of Porsche air cooled engines. it's original purpose was pipe flange sealing without gaskets. The nice part is that it has an unlimited open time (cures via absence of oxygen) and the squeeze out inside the engine remains uncured and washes out with the oil.
Larry
Larry
Hi, I just received a FAA service bulletin on RTV sealant it is NOT approved on Continental motors and I would think Lycoming would apply as well. NE-16-13.pdf
https://mail.google.com/mail/u/0/#inbox/15357d1c527182d4
Hope it work`s Russ Emick,Jr
https://mail.google.com/mail/u/0/#inbox/15357d1c527182d4
Hope it work`s Russ Emick,Jr
Norcalrv7
Well Known Member
I think we can all agree that this is not an approved method. It's fun to think about trying some other options though. That being said, mine is going together with OO silk thread per Lycoming...
Caleb
Caleb
Lionclaw
Well Known Member
RTV-102 is approved for Lycoming per SI 1125D. I used Loctite 518 when I built my engine up the first time and had a few small leaks. After a rebuild a few years later I used RTV-102. It didn't leak after that...
hgerhardt
Well Known Member
I used Loctite 518 on mine 8 years and ~700 hours ago and it's still dry.
Lionclaw
Well Known Member
I think my leaks started when I removed a few case bolts near the front main bearings to install a bracket for the Lightspeed EI. There was a popping sound which was likely the seal failing.
BillL
Well Known Member
Are you referring to Permatex #3? I built over 200 VW engines ('73-'75) with it and never had a leak. In the dealer shop I managed, never saw a case leak with it either. But - that is not a very highly loaded engine, but in South Alabama they got plenty hot driving down the interstate WOT. Other gaskets leaked but rarely the cases, and that was due to other factors, not sealant. Also, the engines seemed to be about a 40-50k engine (~1000hr), so they really were not that durable if driven hard.
Everything has its limits, what does the Lycoming engine school recommend now?
Lycoming school recommends permatex and silk thread - done right, it doesn't leak. They mention the RTV 102 and Locttite becasue they are in the Service Letter, but the skinning issue tends to make them less reliable unles you close the case quickly - and that is fraught with peril. Better take the time to do it right rather than trying to hurry up to beat the sealant cure.
Paul
hgerhardt
Well Known Member
That's only true for the silicones... the beauty of the anaerobics like 518 is they only start hardening once the case halves are assembled, so you could leave the case open for days and it won't harden. And the squeeze-out inside the case never hardens and gets washed out with the motor oil.
Also, lycoming's SI says Loctite 515 is the approved anaerobic, but if you look at the Loctite data sheets, 518 is better suited for aluminum, which is why I used that instead.
And, should explain the proper way to apply 518. Don't smooth it with your fingers. Just apply a 0.1" dia bead and assemble. If you smooth it out, it will tend to trap air bubbles within the flange surface which will compromise the seal integrity. Don't worry about squeeze-out- it will never harden, so it won't clog anything.
Heinrich
Last edited:
fixnflyguy
Well Known Member
Hylomar and silk
I always use Hylomar..never a problem. I have heard equivalent results from Yamabond. I am not a fan of RTV's and cringe using them on my car engine, but they will fill gaps . Case halves have virtually zero gap, and the thread itself probably does the most. Hylomar seems to stay almost tar like for years and works with the expansion/contraction.
I always use Hylomar..never a problem. I have heard equivalent results from Yamabond. I am not a fan of RTV's and cringe using them on my car engine, but they will fill gaps . Case halves have virtually zero gap, and the thread itself probably does the most. Hylomar seems to stay almost tar like for years and works with the expansion/contraction.
