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I'm not super stressed about it. The hole is well above the oil level, and it's not a ton of oil leaking from there- although it's more than can be ignored. Even just threading in a rubber bung from my cold brew coffee maker a few threads stopped any oil coming out when I was out riding it. I don't think it will take much to seal it, but if there is a best option here I'd like to see what people say. Thinking maybe one of these as a plug and some permatex-

That plug / screw you show would be a perfect match--again the key to me would be you want the depth of the plug to exactly match the depth of the hole--& you would have to know the depth of the threads as well--I dont know if that hole is threaded all the way down. and if you are talking about permatex RTV sealant --I would want something more permanent that will not removable ie. seal it forever. --or put the rear brake rod setup on the bike & seal the living hell out of that hole--That could do 2 things at once
 

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So theoretically the deepest part of the hole has been pushed back enough to develop a crack probably on the side beyond the threads or you could see it. It maybe just when the bike is running the combo of vibration and crankcase pressure will release a couple drips. It seems to me that you have to secure that deepest pocket from breaking loose into the engine so a blob of goop that bonds tightly to aluminum is required. JB Weld is aluminum based. It's not enough to plug the hole, you've got to secure the break in place
 

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So theoretically the deepest part of the hole has been pushed back enough to develop a crack probably on the side beyond the threads or you could see it. It maybe just when the bike is running the combo of vibration and crankcase pressure will release a couple drips. It seems to me that you have to secure that deepest pocket from breaking loose into the engine so a blob of goop that bonds tightly to aluminum is required. JB Weld is aluminum based. It's not enough to plug the hole, you've got to secure the break in place
correct I would want the end of the plug basically married to aluminum at the bottom of the hole, and create a complete seal. What I would worry about the most is that the crack would expand during riding due to heat (thats when it leaks). and when it cools the crack closes back up. Part if me would want the threaded plug made of aluminum rather then steel-being that dissimilar metals expand & contract at different rates- an aluminum threaded plug permanently bonded in the hole should reduce the difference in expansion & contraction. At least thats my O.P.O.
 

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Go to a Dodge dealer and get a tube of Mopar RTV , MS-GF-41-B. P/N 05010884AD. Clean the hole with brake cleaner and wipe it dry, and seal the hole with the RTV and install a bolt and flat washer, or red fiber washer. The hole will never leak again, the bolt won’t come out on its own. What could be better.
 

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Mopar RTV , MS-GF-41-B. P/N 05010884AD
Impressive stuff used for tranny gaskets, according to the MSDS it also sterilizes frogs at twenty feet (Octamethyl cyclotetrasiloxane ).

I think this application needs bonding with the aluminum permanently, not a removable gasket material. But thanks for the tip, those frogs in my backyard get a little uppity in the springtime. Well, actually they are toads, psychotropic toads that my dogs like to lick and go crazy. Whacked out pair of 100lb pit bulls are a very impressive force of nature, will make you question just where on the food chain hierarchy you really are.

*Edit - seriously the problem as I see it is not a drop or two of oil on the ground to prevent, its to eliminate the possibility of the thin aluminum case at the bottom of the bolt hole from being sucked into the engine since at this point it is confirmed broken.

Nobody wants to talk about splitting the case and welding the crack from the other side and rightfully so - I think there are other effective solutions if taken right away before it is ridden any more.

Another 2 cents - the underslung rear brake with its torsion rod is not all that great in any way you could measure its performance, and I know it is a pain in the ass to use a normal rear swingarm stand with, so you would not be giving up any useful option in plugging that hole up. And the next time that engine needs to be supported outside of the frame do use a couple of rods through the frame mount holes instead of these like the PO did.
 

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If you use the RTV and fill the hole the cracked metal at the bottom of the hole will never go anywhere. Never. Ever. An easy fix shouldn’t be confused with a bad fix. This is the stuff they use on your brand new car when you take it back complaining of a tranny leak. Ford has the same thing , called “ Heavy Drip Check Sealer” it is tough and dries harder than normal RTV. It is impervious to most chemicals and lubricants once cured. I had a push rod tube leak on my Triumph. I sprayed it clean with brake cleaner and smeared some on the leak. Pretty half ass, really . It lasted four years and started seeping a little. Last winter, rather than pull the head, I just did a better job of cleaning the area and used it again.
 

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My concern would be why is it leaking? If something cracked the case will it lead to a growing split and be a problem down the road, hard to know. I have seen/dealt with porosity in cases that we fixed by cleaning and degreasing the part, then the aluminum was heated and green loctite was applied. The loctite wicked into the pores of the aluminum and stopped the leak. option 2 is to add a brass/aluminum plug and have it blue loctited. This will allow growth and should continue to seal, bigger issue would be later owners removing the plug not knowing why it is there.

I would inspect for the location of the crack and try a sealer, if that does not work I would have a good welder fill the hole and then re-tap if needed.
 

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Discussion Starter #30
Do you think a threaded insert/plug is sufficient or would I be better off with whatever additional sealing I could get with a washer and bolt against that machined face?
 

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I would use an aluminium plug / bolt--measure the depth of the hole carefully -it should be around 22 mm deep-I would personally rather use a plug -this would be for look only--if using a bolt I would for sure use a washer under the head--again measure the depth carefully-I would want the plug / bolt to go in to within 2 mm of the bottom of the hole, use the blue locktite to make a seal--Under no circumstances can this plug / bolt bottom out in the hole otherwise you could damage the case beyond reasonable repair. be careful and measure at least 2 times and dont make a mistake
 

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Discussion Starter #32
Yes, whatever I end up using would be well clear of the end of the threads so I’m not putting on pressure on the back of the hole.
 

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If you could find a really good welder --not Bob under the shade tree lol--you could drain the oil, - clean the living bejesus out of the hole, then clean it 2 more times, get the welder to get down to the bottom of the hole & weld it shut, lets just say for a number --say put 5 mm of weld in the bottom of the hole-that would seal it up-then you could drill & retap the threads down to that point--yes you would lose say 5 mm of depth in that hole--but it is about 1 inch deep and I doubt 5 mm less would make any difference-even if you wanted to add the under slung brake setup--the key here is to seal it permanently so it never an issue
 

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I don't disagree with the welding approach and if you can actually SEE a crack in there it should be the only way to deal with it, imo. However, porosity of thin aluminum is a thing, and you are only seeing a few drips so some other options are still open to you I think. Any serious crack there would pour oil out and you are not seeing that.

Bolt, insert, either one, but I'm thinking bolt as it is easier to drill a tiny hole through the center to let air and excess caulking of your choice escape as you screw it in. Dodge brand froggie neutering RTV, blue Loctite, or even JB Weld would probably work fine as long as the bolt does not bottom out. I suggest drilling a hole in an aluminium or brass, bolt or insert, to make sure that pressure from the air pocket and sealant at the bottom is relieved and not pressing in on the cracked area as you screw it in -IF it is cracked. It would also give a path for the sealant to bond from the case to deep into the bolt for heat expansion.

If the oil is just seeping in from a porous spot in a thin area of aluminum any of the solutions offered will work, the drilled out option would anchor the bottom preventing it from having an air pocket which could under heat expansion break contact enough to release a piece of the thin area into the engine if it does actually have a tiny crack. Using a drilled bolt is also a more accurate way of gauging how much goop to put in too as any excess will squirt out the hole to be wiped off .
 
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