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Rear main seal leaking
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aeromech
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PostPosted: Fri Apr 12, 2013 9:00 am    Post subject: Reply with quote

I love your hightop BTW!

Wasn't mine. I just did the restoration.
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Dogo
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PostPosted: Mon Aug 21, 2017 6:53 am    Post subject: Re: Rear main seal leaking Reply with quote

I pulled my motor for other reasons other than the seal, but it did seem like I had a bad leak coming from it. Replaced it with a red (silicone?) one. And new O ring. It didn't have a paper gasket, so I didn't reinstall one.
I realize now, after reading this thread, that I did a few things wrong (or did I?). Installed it virtually dry. Tapped it all the way in, not flush with the case. And forget what else.
I'm getting ready to pull it again, but I want to rule out blow by before doing so.
I feel no pressure at the oil filler. It actually feels like a slight vacuum. My case is vented to one of the carbs (dual Kadrons) from the oil filler vent.
Here are my numbers. Safe to say it's NOT blow by?

Comp test:

#1: 130
#2: 138
#3: 150
#4: 149
1 and 2 were tested warm. 3 and 4, hot.

Leak down:
I fucked up and didn't adjust valves first. I'm hoping most of the 10% diff at #1 is a tight exhaust?

#1: 10%. Leaks to case and a little to exhaust.
#2: 2%. Leaking to case.
#3: 2%. Leaks to intake/carb.
#4: 1%. leaks to case.

1 and 2 tested warm. 3 and 4, hot.

Thanks for any input in advance.
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aeromech
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PostPosted: Mon Aug 21, 2017 7:58 am    Post subject: Re: Rear main seal leaking Reply with quote

So basically you're trying to locate an oil leak in the flywheel area and you are ruling out breather pressure as the cause because of the excellent compression test readings you've found. Add some engine pics here and tell us more about your engine. Size, age, who did the last rebuild, etc. Also, when you had the flywheel off did you see anything like cracks in the case or a leaking oil gallery plug?
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Dogo
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PostPosted: Mon Aug 21, 2017 9:07 am    Post subject: Re: Rear main seal leaking Reply with quote

aeromech wrote:
So basically you're trying to locate an oil leak in the flywheel area and you are ruling out breather pressure as the cause because of the excellent compression test readings you've found.


Yes, basically. I assume the 10% leak is nothing to worry about (as far as blow by is concerned)?


aeromech wrote:
Add some engine pics here and tell us more about your engine. Size, age, who did the last rebuild, etc. Also, when you had the flywheel off did you see anything like cracks in the case or a leaking oil gallery plug?


Engine was removed, mostly, for a transmission rebuild. As far as I know and can tell, its stock displacement. Previous owner had it rebuilt (PO supplied a receipt for a "1600 short block" from a mechanic shop).
I've owned it for about 4 years. It's not driven much, and neither was it by the PO.
I don't see any leaks elsewhere, now. Oil galley plugs seemed ok, as I remember. No cracks in case. I did not check the flywheel or seal area for inconsistencies as I should have. I replaced some gaskets and seals while it was out. Replaced all bad and missing tin. I also installed a T4 cooler conversion shroud.
The leak is much worse than what it looks like in this pic of a few drops on the ground. I'd say a drop every 2-5 seconds
One thing to point out is that it leaks a lot while running, even at idle. Leak is basically gone after a while of shutting it off

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aeromech
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PostPosted: Mon Aug 21, 2017 9:16 am    Post subject: Re: Rear main seal leaking Reply with quote

Try and check the end play by moving the crankshaft pulley in and out. You basically shouldn't feel much movement at all. Did you look at the flywheel snout which rides against the main oil seal? Sometimes these wear and can leak.

That looks like an aftermarket oil filler/breather (chrome). Does the engine leak oil at idle or only after a hard run? If at idle then I'd rule out the breather causing it.
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SGKent Premium Member
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PostPosted: Mon Aug 21, 2017 9:43 am    Post subject: Re: Rear main seal leaking Reply with quote

if the seal is installed only flush it rides too far up the shoulder on the flywheel and fails. If it was installed dry it likely burned the sealing surface when it first started up. It needs to be installed all the way in, and with some oil or grease on it.
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Tcash
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PostPosted: Mon Aug 21, 2017 12:17 pm    Post subject: Re: Rear main seal leaking Reply with quote

Check end play as posted.

Always use a new seal. Don't reuse the seal you pull out.

And new O ring. It didn't have a paper gasket, so I didn't reinstall one.
No paper gaskets are used with an O ring.

Tapped it all the way in, not flush with the case.
The seal is actually recessed about a 1/16.
Take a look at where the seal rides on the flywheel. If there is a visible line. Polish the surface and install the seal recessed 2/16. So that it will ride on a new surface on the flywheel.

If you have a sand seal. Do a search for crankcase venting with a sand seal.
The oil fill breather is not adequate enough to vent the crankcase.

If you want to double your chances of it not leaking from the crank pins and mating surface. Put the flywheel on, snug the gland nut up. Pull the gland nut off and wick some green 290 loctite sleeve retainer, on the pins and where the flywheel meets the crankshaft.

I highly recommend getting a seal installation tool. I've tapped them in over the years. But had one that leaked. The money spent on the tool is not worth the time of pulling the engine.
https://www-cartersaircooled-com.myshopify.com/pro...ation-tool
https://www.appletreeauto.com/FLYWHEEL-SEAL-INSTALLER-TOOL-7035/

Good luck
Tcash
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Dogo
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PostPosted: Mon Aug 21, 2017 12:56 pm    Post subject: Re: Rear main seal leaking Reply with quote

aeromech wrote:
Try and check the end play by moving the crankshaft pulley in and out. You basically shouldn't feel much movement at all. Did you look at the flywheel snout which rides against the main oil seal? Sometimes these wear and can leak.

That looks like an aftermarket oil filler/breather (chrome). Does the engine leak oil at idle or only after a hard run? If at idle then I'd rule out the breather causing it.


End play was spot on at .006.
When looking at the flywheel snout, what am I looking at to determine wear? Do you mean obvious grooves, or is there a way of measuring consistent/even wear?
I couldnt tell you if the breather is aftermarket. I assume so, being chromed.
It leaks at idle as well.
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PostPosted: Mon Aug 21, 2017 12:57 pm    Post subject: Re: Rear main seal leaking Reply with quote

THank you TCash and SGKent for the tips
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PostPosted: Tue Aug 22, 2017 7:51 am    Post subject: Re: Rear main seal leaking Reply with quote

Quote:
End play was spot on at .006.


I believe that is the wear limit. Next time shoot for .003" to .004". Using a dial indicator with a magnetic base will make it very easy, and very accurate. HF has them very reasonable these days. You don't need anything of Starrett quality for checking that.
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PostPosted: Tue Aug 22, 2017 11:12 am    Post subject: Re: Rear main seal leaking Reply with quote

The spec is .003"-.005". Wear limit of .006".
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aeromech
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PostPosted: Tue Aug 22, 2017 11:32 am    Post subject: Re: Rear main seal leaking Reply with quote

Do you mean obvious grooves

Yes. Flywheels can become grooved where the seal rides against the snout. Maybe you should try some UV dye in the oil. Get a black light on there at night and the leak will stand out. I'm thinking cracked case or oil galley plug behind the flywheel.
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airkooledchris
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PostPosted: Tue Aug 22, 2017 1:05 pm    Post subject: Re: Rear main seal leaking Reply with quote

aeromech wrote:
Do you mean obvious grooves

Yes. Flywheels can become grooved where the seal rides against the snout. Maybe you should try some UV dye in the oil. Get a black light on there at night and the leak will stand out. I'm thinking cracked case or oil galley plug behind the flywheel.


X2. just dye the oil. Once you start tracking a leak this way, you won't bother doing it any other way anytime it's a question of source.
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PostPosted: Sat Sep 09, 2017 5:13 pm    Post subject: Re: Rear main seal leaking Reply with quote

Thanks everyone for your help.
Finally got around to pulling the engine. I also dyed the oil. I think I found the culprit. The Oring was pinched and crushed.
Is it possible to have such a big leak (I mean I was leaking A LOT!) from just the O ring?
I believe the seal looks good and so does the flywheel mating surface. It's no mirror finish but looks smooth to me (please let me know your thoughts).
I also noticed one of the pins seems to be a little shorter. Normal?

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PostPosted: Sat Sep 09, 2017 5:56 pm    Post subject: Re: Rear main seal leaking Reply with quote

Make sure the three other dowel pins are not too long.
Put the flywheel on without oring and tighten the gland nut up to seat the flywheel onto the crank. Pull the nut off and inspect the dowel pins. The dowel pins should not protrude, or be flush with the flywheel surface. They should be recessed at least a 1/16" in the hole.
If not when you torque the gland nut down, The gland nut washer bottoms out on the dowel pins and the flywheel remains loose.
If the one dowel is shorter it is ok.
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PostPosted: Sat Sep 09, 2017 6:37 pm    Post subject: Re: Rear main seal leaking Reply with quote

Will do. Thank you.
Everything else seems ok (other than the o ring)? ....Anyone

I also just realized I have two shims as opposed to three. Three is the norm, correct?
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PostPosted: Sat Sep 09, 2017 6:49 pm    Post subject: Re: Rear main seal leaking Reply with quote

three and wipe the end of the crank off. There is a piece of debris in your photo that will interfere with the flywheel to crankshaft mating flush.
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