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I bought a 2004 Subaru Impreza Outback Sport (2.5L EJ251 SOHC) a year ago and have found a leaking crankshaft seal. When going in to replace it, I see that the leak is probably caused by a small gouge (~ 1x1x2 mm) in the aluminum engine block on the sealing surface, toward the front of the block.

The repairs I feel I can do myself given my tools and experience are to

1. pound the seal into the shaft housing deep enough to clear the gouge, which would be about 2-3 mm deeper than flush. would this cause a problem? seems like there's plenty of space back there ...

2. fill with epoxy and file smooth with emery cloth. i've heard that JB Weld might do the trick, but also hear concerns about aluminum expanding differently than the epoxy. i don't want to cause more problems than i already have.

3. both of these?

Unfortunately, i am unable to weld aluminum (or any metal for that matter), so would have to bring to a machinist for this.

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  • Well, since JB Weld will fix a cracked engine block on heavy machinery, of course it will work on your Subaru! Anyway, interested in hearing if anyone has used it for something like this...
    – JPhi1618
    Dec 23, 2015 at 14:21
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    I've used an RTV called Right Stuff. It's very thick and tacky. Apply a little on inside the block and to the seal. Then pound the seal in to the correct level. Allows the RTV to set overnight. Using an epoxy may screw the block up more.
    – vini_i
    Dec 23, 2015 at 14:26
  • @vini_i - Please make that the answer. It is the easiest, quickest, cleanest way to fix this issue (IMHO). How often do you change this seal? Exactly, not very often. If it does need changed again, cleanup and re-application is not an issue. Do it and forget about it.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Dec 23, 2015 at 14:32
  • Agree that RTV could be used but would love to see a picture of this if it's not to painful to take it. Have you verified that there is nothing raised up from the gouge that could cause damage to the seal when inserting it? Sometimes it's actually difficult to tell.
    – DucatiKiller
    Dec 23, 2015 at 15:05
  • @DucatiKiller - Even so, if it is raised up, running a file over it a couple of times would take it down, then using the RTV to seal it up ... it's the way to go.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Dec 23, 2015 at 15:26

2 Answers 2

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Many times in the past I've used an RTV called Right Stuff. It is very thick and tacky. Degrease everything then apply the RTV to the block surface and a little to the seal all the way around. Pound the seal in to the correct depth. Allow to set overnight.

This solution has the lowest risk of screwing anything up. If the repair doesn't hold then the RTV can be removed easily. Applying the epoxy is much more dangerous. Applying is smoothly is difficult on a rounded surface and sanding may distort the roundness of seal surface.

The RTV can seal minor imperfections in the sealing surface and if the seal is not a tight fit it can glue the seal in.

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  • I think the product Right Stuff is too thick and permanent for this application. Regular high temp RTV would be better, IMO. Its also less expensive.
    – race fever
    Dec 23, 2015 at 18:18
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The gouge probably came from somebody removing the seal with a screwdriver or pick. Not a big deal and very common. The fact that the seal was leaking does not mean that the gouge is causing it. Those seals expand very well and the OEM Subaru seals are really good.

I would lightly (very lightly) sand the gouge with a very fine sandpaper. Then I would install the seal and forget about it.

What if you want to make absolutely sure and want to sleep at night?

Put a little JB Weld on it with a toothpick. Then with the same very fine sandpaper light (very lightly) sand it smooth. Install the seal and enjoy your new found peace.

What if you don't want to use JB Weld?

Some high temp (the red one) RTV will work fine. Also use a toothpick to put in just enough to cover the gouge. Don't put too much or it will be hard to remove if it ever starts leaking again (due to something unrelated to the gouge). Install the seal without waiting for the RTV to set (or wait, won't make a difference).

But I want to use lots of RTV!

Well, knock yourself out.

Just make sure the RTV doesn't fall in the inner seal area!

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