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Old 04-15-2012, 02:27 PM   #1
Team Scream
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Default Case Halve Sealing

I have often wondered why we need to apply sealant to the crank main web surfaces when we seal the engine cases during a build.

Is it just so that there is uniformity between the outer surfaces of the case and these crank web areas with regard to sealer thickness (as if there was a gasket in place)? Or are we actually sealing something here?

The FSM calls for it, but cautions us against allowing sealer to ooze into the bearing or o-ring areas.

I have really scrutinized the cases and believe that there is no real reason to have sealer here other than to provide a uniform thickness across all mating surfaces.

Can anyone shed some light here for me? I would rather not use sealer in these areas if not necessary for actually sealing something.... unless I am missing something here??

Here is a pic of what I am talking about from the FSM.. The green highlighted area are the instructions given. The RED dots I added are the webs that the FSM suggest we add sealer as well as the entire perimeter of the mating surface of the cases.

Do we REALLY need to add sealer right near the crank main journals/bearings?

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Old 04-15-2012, 02:44 PM   #2
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Default

Good question. I think your on the right track.

My best guess is that its a second line of defense to keep the coolant out of the oiling system?

I've pulled a few of those bolts off before only to hear a nice gush of air come out. I assumed it was because some of the coolant evaporated inside the bolt holes
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Old 04-15-2012, 02:51 PM   #3
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i think its required to keep oil from getting into the bolt holes.
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Old 04-15-2012, 03:12 PM   #4
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Quote:
Originally Posted by jesterjames View Post
i think its required to keep oil from getting into the bolt holes.
This^

because of crankcase oil pressure that close to the bearings it could get into the bolt holes and cause a leak into the coolant system. Yes there are washer/seals on those bolts but its better to be safe than sorry. Thats quite a bit of work to have to go back and do over such a quick and small amount of sealer that if wasnt in place could cause a major issue. The washer/seals could also fail over time or if re-used and that could cause the contamination. Id hate to go start my car after it sitting over night to find out my crankcase has filled with coolant.

Last edited by UK-Wagon; 04-15-2012 at 03:20 PM.
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Old 04-15-2012, 05:28 PM   #5
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Quote:
Originally Posted by jesterjames View Post
i think its required to keep oil from getting into the bolt holes.
^^^ agreed, plus added protection if somehow coolant got around the washer and into the bolt hole, then leaking into the crankcase. This would obviously only happen if the washer didn't have a good seal between the bolt,washer, and block.

Edit: I see ukwagon said the same thing

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Old 04-15-2012, 11:53 PM   #6
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Quote:
Originally Posted by jesterjames View Post
i think its required to keep oil from getting into the bolt holes.
I approve of sir JesterJames' logic.
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Old 04-16-2012, 12:04 AM   #7
wrxsubiemod
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I wouldn't be so much worried about the oil getting into the bolt holes as I would coolant getting into the crank case or even around the bearings

Just as bad as a blown head gasket in my opinion
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Old 04-16-2012, 12:54 AM   #8
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On a related topic, I assume all 10 of the case bolts that go inside the case at some point are supposed to have washers?
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Old 04-16-2012, 06:26 AM   #9
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yes. iirc they should be slightly fatter than the head of the bolt too.
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Old 04-16-2012, 01:45 PM   #10
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Quote:
Originally Posted by aboothman View Post
On a related topic, I assume all 10 of the case bolts that go inside the case at some point are supposed to have washers?
Yes and you'll notice the one's internally have sealing washers. Note the rubber used in them.
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Old 04-16-2012, 03:15 PM   #11
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Quote:
Originally Posted by 3MI Racing View Post
Yes and you'll notice the one's internally have sealing washers. Note the rubber used in them.
Which is why I wonder just how important that sealer between the main webs is.
If you use brand new OEM washers then nothing can get from the inside out (oil), or outside in (coolant).

Re-using old sealing washers is never a good idea, and I never would, but I would like to eliminate the sealer @ the main webs if possible...

That sealant is always squeezed out and potentially ends up in the main bearing(s), particularly the ones with an oil groove, which to me can be more trouble than not using sealer there at all.

I guess my question is has anyone NOT used sealer on the places I indicate, and had zero negative issues as a result?
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Old 04-16-2012, 03:31 PM   #12
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Quote:
Originally Posted by Team Scream View Post
That sealant is always squeezed out and potentially ends up in the main bearing(s), particularly the ones with an oil groove, which to me can be more trouble than not using sealer there at all.

I guess my question is has anyone NOT used sealer on the places I indicate, and had zero negative issues as a result?

We only use it around the holes, I don't put it anywhere near the bearings.

FWIW
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Old 04-16-2012, 05:50 PM   #13
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Quote:
Originally Posted by 3MI Racing View Post
Yes and you'll notice the one's internally have sealing washers. Note the rubber used in them.
Ya I ask because I bought new bolts/washers for this bare block I have, and the dealership only sent me 5 washers :| I am not taking the block apart prior to rebuild, so I have no point of reference.

TS: I assume you are speaking of a thin bead of sealer, as opposed to a spread out bead like you posted in the other thread?
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Old 04-16-2012, 10:02 PM   #14
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I mention the washers as they seals the threaded section. For what it's worth, the RTV does the same from the oil...makes a double seal between coolant and oil.
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Old 11-09-2020, 02:29 PM   #15
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Default Sealant

I realize this is an old thread. One advantage of the recommended sealer is the oximie activator that reacts with metal. I believe this permits greater open time rather than a silicone that skins with air contact. More importantly in the context of this discussion, it is my understanding that any excess will harmlessly dissolve in oil. I can provide a link to a much more in depth on sealants (and thread lockers) if desired, including why oil does not affect the sealant sandwiched between the case halves. Threebond 1215, Loctite 315 & 318, Yamabond 4. My Subaru manual makes no mention of replacing sealing washers, but then it does not specify replacing headbolts either.
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Old 12-04-2020, 10:44 PM   #16
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Quote:
Originally Posted by athensown View Post
I realize this is an old thread. One advantage of the recommended sealer is the oximie activator that reacts with metal. I believe this permits greater open time rather than a silicone that skins with air contact. More importantly in the context of this discussion, it is my understanding that any excess will harmlessly dissolve in oil. I can provide a link to a much more in depth on sealants (and thread lockers) if desired, including why oil does not affect the sealant sandwiched between the case halves. Threebond 1215, Loctite 315 & 318, Yamabond 4. My Subaru manual makes no mention of replacing sealing washers, but then it does not specify replacing headbolts either.
I am not familiar with the other sealers you listed, aside from threebond, so I can't speak for them. What I can say about threebond though, is that I have always experienced the opposite as far as open air time, it is one of the quicker drying sealants I have used especially if it is warm. Resealing the timing chain covers on an H6 in the summer is pretty much a one-shot deal that needs to be done with haste. And again regarding threebond specifically, I can say it does not in fact harmlessly dissolve in oil. Quite the opposite actually LOL, it can and will cause much harm.

As far as replacing the sealing washers, Subaru isn't the best with pointing that out. Sometimes with an o-ring for example, they will say to replace it in plain text, but other times the part in question will be marked with a star only in an exploded parts diagram, with the star indicating it as a one-time-use part.
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