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Recommendations For Engine Building Sealant.


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#1 SolarB

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Posted 09 July 2020 - 09:11 AM

Last time I rebuilt my engine and gearbox I used a Loctite sealant. I forget which number but I researched my options before selecting that particular sealant.
I used the sealant without gaskets on the differential case/gearbox interface and the pivot pin for the lever rods. Unfortunately the gearbox leaked from these location from day one. I assume it was either a bad batch or a poor fake as the surfaces were flat and scrupulously cleaned before assembly.

Everything is in pieces at the moment for a rebuild but I will be needing a sealant soon. Are there any recommendations for a sealant that will be suitable for this application?

 

I'm aiming for a 100% oil tight A Series this time.

 

Well, for a while at least. :proud:

 



#2 whistler

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Posted 09 July 2020 - 10:54 AM

I am not an engineer. Some of the later diff cases did not use a gasket but most out there do. A gasket adds distance between 2 components. I may get shot down in flames over this but I think that if you leave out the diff gasket then when you torque up the case the diff output bearings might not allow for a face to face meeting of the two halves of the case. I think this might cause distorsion and the inevitible oil leak.

Over to the engineers amongst you all.



#3 GraemeC

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Posted 09 July 2020 - 11:00 AM



I'm aiming for a 100% oil tight A Series this time.

 

Well, for a while at least. :proud:

 

That's easy - don't put oil in it!

 

 

Yes, some diff casings need gaskets, some don't.  And if assembled the wrong way round it will leak.

Generally if the diff case is held on by bolts then no gasket, if held by studs and nuts then gasket.  However this isn't foolproof as a) it wasn't always the case and b) after 20+ years the hardware may have been changed by a previous keeper.

 

For the cases I have without a gasket I use nothing fancier than off the shelf RTV sealant. 

 

The pivot pin uses an o-ring and I've never used any sealant here not had any leaks.



#4 wile e coyote

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Posted 09 July 2020 - 01:31 PM

I last used Loctite 5940 and engine hasn't lost a drop through leaks since - I mark that down as my crowning a series achievement!! Having said that - at the risk of being utterly patronising (sorry!) much is down to using just enough and not too much a smooth "smear"on the spotless mating surface tracking both inside and outside of bolt / stud  holes followed by even and incremental tightening to spec and the prompt "blending in" of any ooze surplus is what I attribute oil tightness to....I'm a bit of an obsessive about it

 

If by pivot pin you're referring to the rod change seal then minispares do a very effective and reasonable repair kit as:
 

http://www.minispare...ic/MSSK050.aspx

 

.... needs no sealant, a smear of oil round the O ring to ensure smooth fit all that's needed....



#5 GraemeC

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Posted 09 July 2020 - 01:45 PM

I think he means this:

http://www.minispare...|Back to search

 

Which seals with this:

http://www.minispare...|Back to search



#6 SolarB

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Posted 09 July 2020 - 02:19 PM

Gearbox was out of a 1984 Metro. Differential casing has bolts and no gasket when I got it. I assembled it following a build guide Guessworks produced a while ago and was happy with the way it went together.

 

GraemeC - Bell crank pivot pin, that's the name. I don't remember an O ring, then again it was a while ago when I rebuilt the thing. Will make sure I have one this time.

 

Will look at RTVs and the 5940.

 

Thanks for the replies folks.

 

 



#7 Spider

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Posted 09 July 2020 - 07:38 PM

Here you'll find the Factory Advice on the Diff Cap, which doesn't seem to be in any of the Mini Workshop Manuals;-

 

http://www.theminifo...kets-important/

 

I've use Dow Corning and Loctite RTV Sealants on these, but I've also been sure they are for Oil.

 

But, there's so much more to making these Engines and Gearboxes leak-free than Gaskets and Sealants, it can be a lot of work, but yes, you can actually get them leak free and for quite a long time.

 



#8 Cooperman

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Posted 09 July 2020 - 10:32 PM

For the normal gaskets such as timing cover, water pump, oil pump, transfer case, block to gearbox, diff output covers, etc, I use Blue Hylomar (as developed for the Rolls-Royce Merlin engines). For the half-moon oil seal and diff casing seal I use black RTV 'Instant Gasket'.



#9 steeley

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Posted 10 July 2020 - 05:23 AM

I use Loctite 5940 



#10 Richard1

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Posted 11 July 2020 - 03:18 PM

I put Gasket Shellac on everything. sealed for life. 

 

Some people use grease, but since it dissolves in oil, they end up with leaks.






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