Exhaust Exhaust Leak Smoking Me Out..

Discussion in 'SN95 V6 Mustang Tech' started by yz250f49, Jul 2, 2014.

  1. Has anybody ever had an exhaust leak emanate from the beveled flange joint where the end of the header pipe pictured below, mates to the front part of the cat converter pipe?

    I started hearing the exhaust leaking under acceleration yesterday on the way home, and the fumes were coming inside the car.

    I'm told there is not a flange gasket on these, only the beveled fit to prevent leaking. See attached.

    I just tried to snug these flange bolts up, but they didn't seem loose, and it made no difference. Can still hear and smell the leak.

    Is it even possible for these to come loose and leak, and has anyone here ever experienced this problem?

    Another thing I noticed is that it almost seems that the leak is originating from the BACK of the engine block, not below it. Does anyone know if there is some kind of an exhaust inlet to the rear of the block that might leak? Been trying to find an aft side pic of my 3.9L V6 on the web, but no luck so far.

    2004 3.9 V-6 @ 160,000 miles.


    Attached Files:

  2. Does it sound like a tick? I ask because when I first got my car it had a leak between my head an exhaust manifold that would tick under mid to hard acceleration. It happened to be one of the bolt holes in the head was strip out . I had to drill an tap it then put a helicoil in it .15000 miles later still no problem out of it .
  3. Hi thanks! No, it's not a tick now, although I think it might have started out as one, but now it's a full blown leak that makes a loud noise under acceleration, and the exhaust fumes enters the interior,

    I loosened the connection from the end of the manifold to the front of the cat pipe and re-seated them, but it made no difference. Now fearing that it is a leaky header gasket.

    Did you get exhaust fumes inside when you had that leak?
  4. No it did not but I always have my Windows down
  5. It didn't matter if my windows were up or down.
    It was a real "pleasant" drive home Tuesday with the high humidity, 90 degree weather, and breathing the carbon monoxide all the way home ha ha....
  6. That sucks, it gets hot like that in south florida to.
  7. So, for the benefit of others who may have the same problem, here is what I found.
    I was able to take it to my mechanic, and he found that the flange that connects the end of the exhaust header to the front of the cat converter had cracked and was leaking. In fact, it fell off when he took off the header to weld it. Was a lot cheaper than buying a new header, so I'm happy

    That's why all that exhaust was coming inside.

    Attached Files:

  8. Was it the passenger side? I have heard that the ac condensation can drip on that side an over time cause problems.
  9. Yes it was. That's exactly what my mechanic said.
    I have the factory drip shield on there that is supposed to prevent that, so he was a bit confused as to why that happened.
  10. That's awesome that you got it fixed. Now it time to enjoy that pony.