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Would you fix a small header gasket leak?

  • Fix the leak you lazy bum

    Votes: 16 80.0%
  • Who cares; small leak, doesn't matter

    Votes: 0 0.0%
  • Bewbs

    Votes: 4 20.0%

Header Gasket Leaking

8K views 3 replies 3 participants last post by  Obeisance 
#1 ·
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?)
 
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#4 ·
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 (http://www.clubwrx.net/forums/engine-modifications/112360-exhaust-torque-specs-re-assemble-time.html) 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
 
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