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Rear main bearing seals.


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I am assembling an engine to put into my TR2. The rear main bearing cap is sealed at each side by a felt strip. A very early workshop manual which I have says to dip the seals in "Shellac" before fitting. A later manual says to soak them with a liquid gasket sealer. Despite being a home mechanic for more years than I like to admit, I have never heard of "Shellac". What is it and is it still available? Can anyone recommend a modern alternative?

 

Many thanks in advance.

 

Les.

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On two occasions, I filled up the grooves in the rear main bearing cap with a blue silicone. After leaving it alone one day, I trimmed the silicone with a knife. The silicone should not be flush, but protruding about 1 mm above the edges of the grooves. So far no oil is leaking.
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Isn't this the seal that most people now replace with the modern seal off a landrover?  (Some would say continuing the link to agricultural vehicles)

 

I may be wrong and miss read the description... I'm thinking of the one just behind the flywheel...

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Hello Les, The Shellac Knotting as it was called years ago is a dark brown liquid ,smells of turps and meths and is oil based I think, we used to use it to glue gaskets together. I think you can still get it at trade decorators supplies. I used red hermatite on my 3 and had no problems (35Kmiles), hope this helps, cheers Paul.
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Hi Les

 

Bin it! Otherwise it will just leak oil again in due course.

 

My 3A rear seal is an alluminium oil seal conversion supplied by Moss, part number: TT1032(s) and not a drop has been spilt since.

 

Mind you, the gearbox and sump still leak; but then again if a TR didn't leak from somewhere, it would be a Japanese or BMW copy!!  :P

 

Cheers

Andrew

 

http://www.zen21606.zen.co.uk/Forum%20Gall...smith_2_big.jpg

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Clive - It's not that seal. This topic started about the seal between the rear main bearing cap and the engine block : each side of the cap is a groove for a felt strip.

The seal conversion kit is something else : it replaces the rope that seals the rear of the crankshat : the conversion kit contains a rubber lip seal with a spring in it to hold the lip in contact with the crankshaft.

Andrew : are you talking about this conversion kit? To replace the same seal that Clive has in mind?

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The seal conversion kit is something else : it replaces the rope that seals the rear of the crankshaft :

Sorry for that : perhaps the standard rear crankshaft seal assembly has no rope in it, it relies on the scroll on the crank.

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There seems to be some confusion about the seal in question. The two lengths of felt are fitted into the two grooves which are machined into the two vertical sides of the rear bearing cap, to seal the cap to the engine block. It's no good having an oil-tight crank seal if the oil can still leak past the bearing cap. This may be the cause of oil in the clutch housing where most TR owners would suspect the scroll seal.The scroll seal or the revised lip seal is something else entirely. I entered "Shellac" on a search and this comes up as a substance used to seal Knots in timber before painting, to prevent "bleeding" through the paint. I think that Paul, (uvc166) is right because the old seals do smell as he describes.
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Guest longjohn

Hi, the same seals are used in a lot of engines fitted to fork trucks, having done many engine rebuilds over a period of 35 yrs i must have replaced hundreds of these strip seals, i use silicone gasket sealer and had no problem with leaks, the engines a usually rebuilt after 4 or 5 years and on strip down the seals are still good.

Dont forget as somone else said to leave the seal a few thou proud of the cap so when tightening up it squeezes the seal into the groove, dontl leave to much though, and remember a tiny blob of silicone on the end of the seal too.

I remember using Shellac at scool in woodwork, we used it to bring out the texture of the wood, personally i would stick to modern sealants like silicone.

By the way, dont be to alarmed at engine rebuilds after 4 or 5 years in fork trucks, they do many thousands of hours in a very short time and are usually completly worn out by then.

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UVC166 is right with his description of smells etc., shellac was used coat upon coat, rubbed and buffed instead of varnish to give a highly polished finish, by French Polishers, before varnish was made, but it is permeable to water.
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This is just to wind Clive up again - anorak's etc!  In the 1927 'Modern Motor Engineer' they mention using shellac as a seal or nellite which I assume was a trade name.  Cannot find any details of it, as Jon said I remember shellac from school days, something to do with french polishing wasn't it?

Nigel

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...........   but does anyone know of a modern substitute which needs to be fluid enough to soak into the felt seal ?
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  • 2 weeks later...

The engine is now assembled and will be in the car this week.

 

I managed to find a tube of "Wellseal" at my local engine rebuilders, which had been left as a sample for them to try out, but they had never bothered, so it became mine for two quid. The length of felt seal was cut into 1" lengths and soaked in the Wellseal, which is very runny. Each piece was then fed into the groove using a thin screwdriver and rammed down hard using a 3/16" square punch, until no more would go in. A very messy job as the Wellseal oozes out everywhere.

 

See you all at Malvern.   Les.

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