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Sealants for machined housings on vtl.

Jerry Murphy

Plastic
Joined
Dec 20, 2018
What sealant can I use to seal covers and housings the parts are machined surfaces. Im using on a bullard vtl have just rebuilt transmission and need to seal the covers and transmission housing on . I have used regular black rtv in the past but with no luck. Any ideals been reading up about diferant types but no sure what to use.
 
How can black RTV NOT work ?

I use the blue stuff with a paper gasket, smear a very light film
on both sides of the paper gasket (automotive applications).

I make it so light the blue sealant is almost clear, too much and it oozes
out (and in as well, not good).
I also let it tack up for 15 minutes or so, before putting on the cover.

While I have not personally changed a Bullard xmission, have seen several apart,
and it looks like a simple drawer.

Did you take a file to the flat surface to check (and remove) any burrs that might
cut the gasket (or keep it from properly seating) ?
 
Call me old school, but I still use Indian Head shellac type sealant, with or without a gasket. Just last year I reworked a finely crafted late 60's German made milling machine X axis drive. Oil filled gear box, motor flange etc. without leaks. Just one of countless successes with the stuff over the years. Works well on closely machined surfaces without a gasket. Doesn't add thickness which in some instances is what you want. Permatex makes a similar stuff called something like Aviation Form-A-Gasket.

Dave
 
I've never been a big fan of RTV type sealants where oil contact is concerned. Never seems to hold up all that well. A better sealant is motorcycle case sealer. Threebond 1184 or Yamabond4 or Hondabond4.

Since I have worked in several aerospace related shops I discovered that they use some excellent sealants in the assembly of components. Boeing BMS5-95 is an excellent case sealant.
 
There is no gaskets for this application. I've tried the rtv in a very thin layer I think the problem is it gets pushed out after the cover is tighten up. If I use the Indian head is it hard to pull apart after it sets also the Yamabond how about it.
 
The motorcycle case sealants are a "semi-drying" type compound. They stay kind of flexible after drying. It will be tough to pull apart after it hardens though. If there are jacking holes or a couple good pry points it would not be bad.

If you need something that does not really harden, then you should use Hylomar Blue
 
Hylomar or Aviation Permatex if you don't want to get too fancy. either will work well. Caterpillar sells a sealant for their final drives where no gasket is used- might be another possibility.
 
Yes the Indian Head and Permatex Aviation harden... kinda-sort-of, over time. But it's the kind of set that will release with a smack or two of a mallet. Or "tappy-tap-tap" as some folks like to say. The stuff that seeps out during assembly can easily be cleaned away with alcohol.
 
I'm a big fan of Hylomar too (after all, if it can keep a Hewland gearbox from leaking, it's worth a look!).

However...

---- Genuine Hylomar is perfect for sealing Hewland bearing carriers and rear covers, or any other parts that need to be disassembled easily and without a lot of scraping to clean up the residue. It is not recommended for semi-permanent assemblies such as Hewland sideplates. Seals gaps up to .010 inch and since it never hardens, it makes disassembly a snap. It cleans up easily with acetone, even after use. Hylomar also makes an excellent gasket dressing. ----

As mentioned though, Yamaha and Honda both sell gray sealants that work really well on engine cases.

PM
 
I hate RTV with a passion, but it can work. You have to use it right. Most guys use way too much and try to fill the cavity with oil too soon.

The best is to use a small bead and let the assembly sit for 24 hours before filling it. When I worked in automotive assembly, all of the engine components that were sealed with RTV type sealants were allowed to sit for 24 hours before being filled.

I like Hylomar or Permatex #2.
 
Thanks for all the help. I think I'm gonna go with the hylomar. Was thinking about that or the permatex 2. Thanks all for you advise.
 
Permatex right stuff...sets in 15 minutes. After resealing an older vmc several times a tech recommended that and it's held up great for 5 years now.
 
Many times RTV fails because the surface finish is to smooth most components made to use RTV as its only method of sealing use a relatively coarse surface finish. Bill
 
I don't know where you can buy Hylomar off the shelf. But, you should find Permatex #2 at any auto parts store.

Thats kinda strange, because over here blue hylomar is the only stuff i can actually buy in this town from the local garage. It works well, but you need good joint cleanliness.

Loctite have zillions of options too.
 
Just a note: After reviewing literature on the Permatex 2 vs Permatex 3 Aviation Form-A-Gasket, #2 application specifications does not include non-gasketed close fitting machined surfaces for which I believe the OP is dealing with, whereas #3 Aviation does.
 
#2 and #3 are essentially the same stuff. #3 is just diluted with some kind of solvent or something to make it a liquid that can be brushed on.

IMO, they can be used interchangeably.
 
Used to be able to get it at NAPA, but I just checked their online store and it does not show up. :confused:

The first time I ever saw Hylomar was at a shop that repaired steam turbines. The maintenance guy I was working with gave me a tube. I've never seen it in a store in my area. I buy it from Zoro/Grainger.
 








 
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