Silicone gasket on Lycomings

[marshmaster pat]

It seems that Lycomings and Continentals and prehaps GPUs are famous for starting to leak oil after a while. Between the cases, at the base of the cylinders, behind mags, and a few other places. Never seems to be the same spot on each engine, but fairly common.

Now I realize that this can be due to the case are no longer true (basically rejected airworthy cases on A/C engines) and this could lead to some leaking. But it is a pain.

What I would like to know does anyone use silicone gasket on the case split on Lycomings as well as the thread gasket? Or anywhere else on their engines? Just curious. Thanks

 

[kb27_99]

Pat,


On a friend of mines 0540 angle valve engine he had a bad leak on the case halfs right in front of the starter. We went to a aviation supply house at the lafayette airport a bought some aviation grade sealer made for that type of application (I'll get the name of it for ya next time i go by there). Cleaned the leak off and put this stuff on and the leak has been sealed for about 80 hours so far.



Kevin

 

[Anonymous]

Aviation Form-a-Gasket?

 

[blackpowderscout]

I'd like to know the name of that stuff too. My 470 loves the oil but since Advance keeps upping the price everytime I get a new case it's time to slow it down a bit.

Adam

 

[pirate]

I asked a friend of mine, Lew Ingle, what he uses. He's been building aircraft engines for airboats in Inverness for twenty years or more. He swears by 3M Rubber Gasket Adhesive #847. You can pick it up at most marina's. After coating the flange on a case he also runs a length of thread completely around it keeping to the inside of all bolt holes. When the case halves are bolted together it crushes the thread and helps seal any pinhole leaks.

Ken

 

[rick]

Pat - When I rebuilt my 4 cylinder a few years back, I was told by an aircraft mechanic to use RTV silicone without the thread.

The crank broke at the prop flange on that motor after about 150-200 hrs. (can't remember exactly), but in that time there was never any leaks between the case.

Also found this on the internet:

"The latest revision of Textron Lycoming Service Instruction No. 1125 specifies POB No. 4 Perfect Seal and silk thread as the generally used items for sealing crankcase finished parting surfaces that do not employ gaskets. Two other products, RTV-102 or LOCTITE-515 applied as a very thin film without silk thread, may be used as alternate materials for sealing crankcase parting surfaces."

Here's the link: http://www.prime-mover.org/Engines/Lycoming/Flyer/Maintenance.html

 

[COLD]

I would think that anything we use in the HD/AUTO market should work nice in airplane. The "Permetex RIGHT Stuff " has worked great! Other stuff is "loctite" fLANGE SEALANTS (Manager buddy at a Train Mtc. Facility gave me it!). AC world has to go through so much stuff that even if they are developing an incredible product, it might cost to much to approve it for every application. I built a couple engines with the flange sealant except for the head gasket. Said that over .050 gap buy and add spray primer. otherwise 0.010 varience. Only thing I have found regarding right stuff compared to the flange sealant is that (while I haven't tried it with primer) on the bigger gaps, right stuff sets up quicker. The work I do, I'll be running " the Right Stuff" in an hour if necessary!

 

[COLD]

The Post before actually came on before I posted. Thats one of the numbers and I have a 518 here and im not sure what else I have in the garage. The one nice thing about this stuff, is that , (while you don't want to make such a large bead lots squiches out!) If it has contact to air, it doesen't set. So if you used silicone you could have a half inch blob where you dont want it. This stuff stays the same way it was in the tube and is just washed away by the fuel or oil... But the stuf's not CHeAp

 

[Des Moines Boater]

When I rebuild aircraft engines I always use the silk thread with Permatex Aviation Fom-A-Gasket. I use Tite-Seal for the crankshaft seal. I learned from a very experienced aircraft mechanic and instructor. These two items are cheap and both can be found at most auto stores. If you still have a leak, you have bigger problems. What you do then is send the case to Divco in Tulsa and they can repair any aircraft case made. Good people and not very expensive. Hope this helps.

 

[Anonymous]

I am very familiar with Aviation Form-a-Gasket, we keep it in stock at NAPA, but not familiar with Tite Seal. Who makes it?

Rick, is Loctite 515 an Anaerobic sealant? Our mechanics love to use that stuff on tractors where the rear end bolts to the transmission and the axle tubes or "trumpet housings". It makes such a good seal that it is hard to get the stuff apart again!

 

[rick]

Had no idea till you asked Red. Found out on the internet, that it was anaerobic. Glad you asked.

The only thing I knew about anaerobic was in the compost pile...stinky stuff there, but it must be what you need with that type of sealant.

 

[jdotson]

I've been watching this thread and wondering if anaerobic sealant was going to be mentioned. I know that is the stuff used when sealing cases on outboard engines....at least on the older Johnsons I've worked with years ago. Wasn't sure if aircraft cases might use it too.