I have a boost leak of the most mysterious variety. When the turbo system (mainly meaning whichever *&%#@ piece of it is leaking) is cold, above 8ish psi it lets loose a noise. This noise is not the typical pssshhhhh that one would attribute to a boost leak, it is more of a high-frequency fluttering sound, on top of the pssshhhh. It is also very loud, underhood, and sounds like it is coming from the left side of the car.

Once the system is warmed up, the noise goes away. I can tell that the leak is still there because the performance is the same. Sluggish response, running rich, etc. The noise comes back after long periods of no boost, like descending at low rpm for 10 miles. It goes away again afer a few boostings.

Due to the temperature dependent nature of the noise, I would guess that whatever is making it is made of rubber or similar.

Tonight I went through all of my vacuum hoses and blew into each one. Nothing leaked. This leads me to think that perhaps it is a gasket somewhere in the pressure side of the intake tract. I can rule out the hose connectors as the noise was present before and after the FMIC install. I checked each one thoroughly for tears upon reassembly. I can also rule out the BPV as it is a Forge piston-type. Has anyone seen an intake manifold gasket (at TB or head) do this? Can you think of any other way to check?

The car holds good vacuum (around 15inHg at 5500 ft), and runs OK, but the leak/performance has been getting worse since I have owned it. Any thoughts are much appreciated, I am at wits end here.

Thanks,
Andy
91 Red SPG
180K
K&N, FMIC, 2.8FPR, 30lb inj, Brad's AID, 2.5in cat back, Forge BPV

posted by 198.11.17...

• OK, I just spent a half hour blowing hoses..., Andy E, Thu, 9 Oct 2003 19:47:02 <-- Viewing This Message
  • Re: OK, I just spent a half hour blowing hoses..., MS, Sat, 11 Oct 2003 10:42:35
  • Re: running rich???, JohnK, Fri, 10 Oct 2003 09:56:36
  • Re: OK, I just spent a half hour blowing hoses..., soulman9, Fri, 10 Oct 2003 09:09:17
    • Wow, 18-20..., Andy E, Fri, 10 Oct 2003 12:30:11
      • Re: Wow, 18-20..., soulman9, Sat, 11 Oct 2003 08:49:47
  • jazz trumpet, gorper, Fri, 10 Oct 2003 08:32:27
    • Grommets..., Andy E, Fri, 10 Oct 2003 14:42:13
      • Re: Grommets..., gorper, Fri, 10 Oct 2003 15:03:53
  • check your intake hose boots. esp the turbo el. n/m, chrisx, Thu, 9 Oct 2003 20:33:16
    • They are all intact, any other guesses? nm, Andy E, Fri, 10 Oct 2003 01:00:39
      • You've taken them off and rolled them in your hands, RS , Fri, 10 Oct 2003 11:48:48
        • I have..., Andy E, Fri, 10 Oct 2003 12:23:58
          • Dang!, RS , Fri, 10 Oct 2003 12:45:58
            • No plastic on my IC..., Andy E, Fri, 10 Oct 2003 14:40:13
              • Good thought. Maybe not the valve itself, but...., RS , Fri, 10 Oct 2003 15:24:07

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