Oil Leaking

Any topics pertaining to the BMC A-Series engine.

Oil Leaking

Postby johnmcguire » Wed Jan 14, 2015 10:49 am

I have pulled my 948 out of the Mark 1 sprite to replace the clutch plate and oil pump. I have had a persistent and messy oil leak from the rear of the sump since I recently rebuilt this engine. What option has been most effective in stopping this typical leak? Has anyone had good results using the Moss "rear oil seal conversion kit"? What about the "upgraded" neoprene sump seal?
I recall something about a custom kit that required some machining of the flywheel but was helpful.
Thanks, John McGuire
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Re: Oil Leaking

Postby Charlie Tolman » Fri Jan 16, 2015 1:02 am

Is the oil leak at the location where the rear main cap fits against a thick "gasket" in the oil pan?
Or, is the oil leaking past the scroll "slinger" at the rear of the crankshaft ?

Hopefully, some readers can offer advice on the crank seal.

Is it possible that there is not enough venting from the rocker cover, side covers, and/or timing chain cover, so that blow-by pressure is building-up in the crankcase ?

CT
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Re: Oil Leaking

Postby peter an5l » Mon Jan 19, 2015 4:13 pm

Check if the cap for the oil pump on the rear engine plate is soldered all around. Sometimes the solder cracks and oil finds it way and running down the plate.


greetings

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Re: Oil Leaking

Postby admin » Fri Jan 23, 2015 1:11 pm

I've heard good things about the Moss kit, but have never owned/installed one--just second hand opinions. Rear main seal is a leak risk on the A-series...(but you already knew that)
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Re: Oil Leaking

Postby Asolepius » Tue Mar 03, 2015 7:43 am

Only just spotted this thread. I have used the rear main bearing seal kit from the Morris Minor Centre, which is the same as the Moss kit AFAIK. Very difficult to fit, and I had to have the crank flange sleeved to get a decent surface. I have the engine out at present and the lip seal appeared to be leaking. Because of the huge diameter I don't think they last long. Just putting a new one in....

The sump/pan seal is another matter, and a perennial problem. I just found all the screws were not at all tight, and both end seals were leaking a lot. I suspect the long gaskets are quite soft and deform over time, allowing the screws to loosen. I wonder about deleting them and just using silicone sealant. The screws should then tighten up solidly and also nip up the end seals tighter. What do you guys think?
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Re: Oil Leaking

Postby Charlie Tolman » Wed Mar 04, 2015 1:54 am

I have used standard long gaskets for the oil pan, and both cork and neoprene(?) semi-circular short gaskets at the ends. A very thin layer of silicone was applied to the interface of the long gaskets and the oil pan (no silicone on the block). It is important to apply some silicone where the short gaskets and long gaskets come together.

If the problem is related to the long cork gaskets slowly compressing, and the pan bolts becoming loose, then take 10 minutes twice a year and moderately tighten all of the oil pan bolts. Using thick layers of silicone instead of the recommended gasket, usually ends-up as a mess, as evidenced by engines in cars of my friends.

I never had pan gasket leaks with 948 and 1098 engines, but then, they were usually rebuilt after each racing season.

If you really want to employ the "all-silicone" approach, remember that it is a two step process. Apply lots of silicone, align the parts, and lightly tighten the bolts, making sure that the silicon is only slightly compressed, and that it has made contact with both surfaces normally sealed by a gasket. Many hours later, tighten the bolts a little more.

I have seen oil pan bolts loosen due to engine vibrations, requiring drilling and safety-wiring of the bolts. (Not a Sprite engine.)

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Re: Oil Leaking

Postby Jim Gruber » Wed Mar 04, 2015 1:48 pm

Take a look at the kit offered by Gerard C. See gerardsgarage.com web site for details. His kit easier to install than MOSS Kit, no special machining needed, and from all that I have read including kudos from several well known engine builders is the first one that really does work. NFI full details on his Web Site.

Charlie, check this one out. This one is right up your alley.
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Re: Oil Leaking

Postby djimbe » Wed Mar 04, 2015 4:22 pm

regarding oil pan gasket leaks/replacement/etc. the information in this thread

viewtopic.php?f=3&t=4488&p=18434&hilit=oil+pan+gasket#p18434

is worth heeding. Had I not looked for the advice displayed there before changing my pan gaskets I would have screwed up and done it wrong. Fixed my pan leaks right up when I did the job correctly...
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Re: Oil Leaking

Postby peter an5l » Thu Mar 05, 2015 12:54 pm

...as I wrote in that old..old thread. :D Use cork seals and cut them not to size but a little bit longer, so they can compress when putting everything together. And maybe Charlies tip is usefull, I always put everything together when the silikon is wet and wait for 48 hours before start the engine. But first make clear, that the oil comes from the leaking gaskets from the pan. I ve seen so many and had so many backplates in my workshop to repair the cracked solder on the cover for the oil pump ! A common fault !!!!

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Re: Oil Leaking

Postby johnmcguire » Tue Jun 02, 2015 10:07 pm

I installed the Moss kit and there is NO oil leak now.
At the same time I used the neoprene seal and left it and the cork seal at the front plenty long.
So far so good.
Thanks for all the good advice, John
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