R

rivetshaver

Active Member
I am getting ready to reassemble my lyc 0320 d3g the overhaul manual has 3 ways to seal the case joint, silk string and pob sealer, rtv102 and permatex.
I dont have the silk string and pob sealer but I do have a tube of rtv 102. Has anyone used rtv for this step? and what were the results?
Thanks
Gregory Targonski
 
Permatex 3D

When I overhauled my engine some months back we used the Aviation Grade Permatex 3D along with the silk string. I found the Permatex at an O'Reilly Auto Parts. Its the same stuff Aircraft Spruce sells. Even has the words Aviation on the pint I bought.
 
His advice

My AP/IA said the silk thread is the key. The permatek (or whatever you use) is just there to hold the silk thread in place.

He's been assembling engines for 60+ years (FWIW).
 
0-320 case seal

rivetshaver said:
Has anyone used rtv for this step? and what were the results?
Thanks
Gregory Targonski
Click to expand...

For what it is worth, I have been going some issues with an )320 that was leaking at the case 1/2's. After talking to a number of A&P's I am told that the process is very tricky in getting the halves together properly. You have limited time to perform the operation and the silk thread can very easily slip off the flange (which is what happened to mine) in which case it will leak. The secret I have been told is to rehearse the procedure numberous times before hand so you will see all the required angle deflections and twists needed.
Good luck Dr Targonski
 
I helped a friend of mine put the heads and banks together on a Merlin. Over the years one thing P-51 operators have had trouble with is coolant leakage there. The engine builders (Nixon, Roush) have found what works best on sealing mating surfaces is good old-fashioned proseal. That's what I've been using on case halves and haven't had any trouble with it. Silk thread is a pain to deal with, POB #4 will eventually dry out, the Loctite product (hylomar?) sets up quickly so you have to be in a hurry to put the case halves together.
 
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rocketbob said:
I helped a friend of mine put the heads and banks together on a Merlin. Over the years one thing P-51 operators have had trouble with is coolant leakage there. The engine builders (Nixon, Roush) have found what works best on sealing mating surfaces is good old-fashioned proseal. That's what I've been using on case halves and haven't had any trouble with it. Silk thread is a pain to deal with, POB #4 will eventually dry out, the Loctite product (Hylomar?) sets up quickly so you have to be in a hurry to put the case halves together.
Click to expand...

Bob,
Hylomar was actually developed by Rolls Royce Aircraft. It's a thick blue paste which never dries out. It's most commonly marketed by Permatex in most auto parts stores. It allows you to take your time putting the case halve together, as it won't dry [ever].
It's not the same thing as Permatex #2 or Aviation Permatex [neither of which Lycoming recommends]
I can well believe that ProSeal would work great.
Charlie Kuss
 
serpentine o-ring

I recall reading a kitplanes article a number of years back about a shop that had STCs for a bunch of engines to machine a dovetail groove around one case half for a serpentine o-ring. I thought it was a neat idea although my IO-375 will not have such an o-ring (based on Bart's recommendation).

The idea still appeals to the engineer in me.
 
mcencula said:
I recall reading a kitplanes article a number of years back about a shop that had STCs for a bunch of engines to machine a dovetail groove around one case half for a serpentine o-ring. I thought it was a neat idea although my IO-375 will not have such an o-ring (based on Bart's recommendation).

The idea still appeals to the engineer in me.
Click to expand...

Ly-Con in Visalia, CA are the guys doing the O-ring mod.
 
I will have to seal up my case halves as soon as my ECI kit arrives. My concern with using ProSeal is that you may have a terrible time getting it apart at overhaul.

AERO and ECI recommend Silk and Permatex. I have that ready to go, but always interested in a better solution.
 
We must be careful saying "Permatex", a brand name with dozens of different sealing products. Need a product number.

You can't even be sure of product names. Some years back I bought some "Hylomar" at the auto parts store and it was not the classic blue gel. Had to order from an aircraft supply to get the real stuff.
 
Permatex 3D aviation "form a gasket" is what AERO sent me and told me to use.

I can not find any POB #4 "Perfect Seal sealant". The lycoming OH manual says to use "a non-hardening sealant"? That leaves lots of choices.

SI 1125D says to use POB #4 or Loctite 515 or RTV 102 (White Silicone).

To the original post about the success of using RTV 102. I am not convinced that this is a good solution. I am all ears though. Right now I am planning to go with the Permatex 3D.
 
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POB #4 "Perfect Seal sealant" is available. You can buy it from Mattituck, or search the archives, I recall somebody posting an internet source for it some months back.
 
Thanks for the replies, It appears that no one has used rtv 102 during their engine build. It is quiet interesting the varied opinions and variations from specifically approved products and procedures. The concencus seems to be that the string and sealant method is the most widely used. I am leaning in that direction also. Now I need to find some string and POB sealant.

I am flattered to be called Dr. Targonski
 
rivetshaver said:
The concencus seems to be that the string and sealant method is the most widely used. I am leaning in that direction also. Now I need to find some string and POB sealant.
i
Click to expand...

...and its also worth noting that most case leaks happen with engines that use POB#4/string. On one engine certified engine I did recently I used two strands, POB #4 and did everything correct and it still ended up leaking.
 
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Hylormar

I intend to use Hylomar and 2 strings of silk thread as I have yet to hear anything bad about that combination. I like the fact that it allows you more time as it doesn't dry fast....or at all. Silk thread is available from Joanne Fabrics for just a few dollars. Hylomar is available on Amazon.com from various sources.

John
 
There are several Hylomar products...

DanH said:
We must be careful saying "Permatex", a brand name with dozens of different sealing products. Need a product number.

You can't even be sure of product names. Some years back I bought some "Hylomar" at the auto parts store and it was not the classic blue gel. Had to order from an aircraft supply to get the real stuff.
Click to expand...

...but the original stuff is Hylomar Universal Blue.

The Racing Formula is the same stuff with acetone as a solvent...

http://www.hylomar-usa.com/_resources/_html/products.html

It is also Permatex part # 85249.

http://www.permatex.com/products/Au...ng_Formula_Gasket_Dressing_Flange_Sealant.htm

Interestingly enough, one of the main distributers for the Hylomar Blue Racing Formula is Harbor Freight --

http://www.harborfreightusa.com/usa...o?itemid=97824&CategoryName=&SubCategoryName=

Lots of Hylomar info and history at the links above.

http://www.hylomarblue.com/

Many part numbers and options so buy carefully, but this is the original Rolls-Royce developed non-hardening sealant.
Harbor Freight is a good source, but a local airpark resident found it was an on-line order only - maybe a store could special order it?

Your local Grainger store should be able to get the original Universal Blue stuff - imported from the UK according to their info page --

http://www.grainger.com/Grainger/items/2VUV1?Pid=search
 
Hylomar - Great stuff

az_gila said:
.snipped

The Racing Formula is the same stuff with acetone as a solvent...

http://www.hylomar-usa.com/_resources/_html/products.html

It is also Permatex part # 85249.

http://www.permatex.com/products/Au...ng_Formula_Gasket_Dressing_Flange_Sealant.htm

snipped
Click to expand...

Gil,
Wow! Great post with lots of good info on Hylomar. I'll add another. I've used both the original and the Permatex version listed above. Here is a link to the technical data sheet for the Permatex version found at your local auto parts store. See

http://www.permatex.com/documents/tds/automotive/85249.pdf

Charlie Kuss
 
I'm no expert but

I did the silk thread deal at Superior's build school once. It was no big deal at all. The actual mating was done on an engine stand with the crank standing upright. As I recall, we put a dowel through the wrist pin bore and used this to hold the first case half in place. It was easy, but I would want an extra pair of hands and a couple of dry runs before attempting it again. Also, I was told by the instructor that the silk thread provides a gasket of predictable thickness, leaving just the right amount of sealant.
 
Right now the recommended case sealant in the motorcycling world is Hondabond HT. I used it the last time I assembled my Busa motor and it's working fine. Say what you like about Honda, the do know engines. I don't know why it wouldn't work on an aircraft engine.
 
I've got a great running O-360 that someone sealed the case halves with silk thread and I'm sure they also did it correctly and found it not a hard process to do. Leaks like a sieve however.

There is no engine produced today that I'm aware of, other than Lycomings and Lycoming clones, that use this antiquated method to seal mating surfaces.
 
Case on my O-360 leaks just aft of the front seal on the bottom. With UV dye I've verified its not the nose seal leaking. Essentially just below the main bearing.

On the 540 I did last year it leaks slightly just below the flow divider on top of the case. I sealed that one with two strings of silk thread inside and outside of the bolts, POB #4, torqued the case bolts to 100in/lbs.
 
How to fix a case seal leak?

Hey Bob, my 0-360-A1A is starting to leak at the crank case halves just behind the starter mount. I haven't pinpointed the leak yet and it may be the through bolt. What did you do to stop/reduce the leaking?
 
eric_marsh said:
Right now the recommended case sealant in the motorcycling world is Hondabond HT. I used it the last time I assembled my Busa motor and it's working fine. Say what you like about Honda, the do know engines. I don't know why it wouldn't work on an aircraft engine.
Click to expand...

Hi Eric,

I know that you have said in another thread that you are new to aircraft engines - one of the things you'll probably figure out tis that we are dealing antique designs here - not the latest stuff coming out today. The case halves on a Lycoming are machined so that they match exactly - no O-rings or gaskets (other than the specified silk thread). The camshaft rides directly in the machined bore of the crankcase, so if you change the fit between the case halves, you change the clearances of the camshaft bearing.

Which is not to say that alternative sealing machines can't work (many do) - it is just to be careful about using anything that changes the fit (adding space) between the case halves.

Paul (not an engine expert, but have learned a lot from folks that are...)
 
Frank Smidler said:
Hey Bob, my 0-360-A1A is starting to leak at the crank case halves just behind the starter mount. I haven't pinpointed the leak yet and it may be the through bolt. What did you do to stop/reduce the leaking?
Click to expand...

Hey Frank! Likely its because the thru-bolt is not o-ringed. You can just goop up some proseal and cover up the bushing and thru bolt nut.
 
Ironflight said:
Hi Eric,

Which is not to say that alternative sealing machines can't work (many do) - it is just to be careful about using anything that changes the fit (adding space) between the case halves.
Click to expand...

Hi Paul,

The Hondabond HT is similar to Permatex. A thin coat is applied to each of the machined surfaces and when the cases are assembled what doesn't squeeze out cures and seals the cases.

I only mentioned it because it's pretty much considered to be the state of the art product at this time. But I understand that the adoption of new products tends to be slow and for good reason. Better the Devil you know than the Devil you don't.
 
Hylomar

Do you guys recommend putting Hylomar on both crankcase half surfaces before mating or just one?

Also do you think two strands of silk thread is overkill?

I have read different combos, just wondering what method is more common.

Thanks
John
 
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