Header Gasket Leaking

View Poll Results: Would you fix a small header gasket leak?

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  • Fix the leak you lazy bum

    16 80.00%
  • Who cares; small leak, doesn't matter

    0 0%
  • Bewbs

    4 20.00%
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This is a discussion on Header Gasket Leaking within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; If you found evidence that your header gasket was leaking, would you take the time (and risk of shearing bolt ...

  1. #1
    Registered User Obeisance's Avatar
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    Header Gasket Leaking

    If you found evidence that your header gasket was leaking, would you take the time (and risk of shearing bolt off in the engine block) to replace the gasket?



    My car has been throwing the P0420 with increasing frequency, and has high fuel trims (+8 to 12% at idle air loads). I suspect that leaky exhaust may make the A/F sensor read lean, so the car adds fuel, leading to too much carbon for the catalytic converter to handle. (does this explanation make sense given my symptoms?)
    David - '05 WRX

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  3. #2
    Subaru Newb MainFrame's Avatar
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    Risk of shearing the bolt off? I've removed and replaced various headers on my car at least a dozen times and that was never a concern.


    ANY pre-turbo exhaust leak should be dealt with post haste.

  4. #3
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    ^ This, definitely fix it...it's an easy fix and you should have no trouble getting the bolts off. Just hit it with some good penetrating oil and let it soak in, you'll be fine.

  5. #4
    Registered User Obeisance's Avatar
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    Quote Originally Posted by MainFrame View Post
    Risk of shearing the bolt off? I've removed and replaced various headers on my car at least a dozen times and that was never a concern.
    This turned out to be true. Thanks.

    On the other hand, my "evidence" that I had a gasket leak turned out to be a false alarm. Perhaps I was too fast to judge the black crud on the head as exhaust blow-by around the gasket.

    When I pulled off the heat shields and exhaust manifold I saw the dirty spots, but there was no smoking gun:





    No obvious blow by on the gaskets, manifold or on the heads.



    Anyhow, I cleaned every thing up, polished the surfaces which would be re-mated together, and assembled it according to some rather gentle torque specs (Exhaust Torque Specs "Re-assemble time!") with new grimmspeed gaskets.

    Grimmspeed gaskets are thicker:


    Polished surface:


    Then, I made a test run for about 20 minutes to see if everything worked well.

    My boost spools just as fast as it did before (thus I expect that I don't have a new massive exhaust leak).



    My fuel trims seem to have changed very slightly after the gasket change, but I will have to see if this is permanent: I suspect that it is within normal variation. This is, however, the first time since I've been checking fuel trims that my numbers are so close to the acceptable +-5% range.

    Before:
    A/F Learning #1:
    (g/s)0 - <5.60 5.60 - <10.00 10.00 - <50.00 50.00+
    (Fuel trim)6.98 4.1 2.64 -1.86

    After:
    A/F Learning #1:
    (g/s)0 - <5.60 5.60 - <10.00 10.00 - <50.00 50.00+
    (fuel trim)5.03 3.61 0.1 -1.95
    David - '05 WRX

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