Fixing the howling sound in my Porsche 996

By peterm, 20 December, 2017
Porsche 996 headlight

After living with a noise that seemed to come from the right front of the car, I finally dug in and did some research. This noise is described as "howling" you'd hear when you blow air across the top of a bottle. For me, this happens at speeds between 25-40 while running at a constant speed. In fact, one way to confirm is to see if the noise stops when accelerating (it does).

I decided to invest in some basic tools. I bought Wayne Dempsey's book and some basics including a floor jack and stands, breaker bar and torque wrench. I read and re-read this article at Pelican Parts, http://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/106-FUE.... Feeling ready, I got the car up on the stands and started removing the wheel well liner.

I got the fuel vent valve replaced but missed the fact that there was a reed switch that fitted into the valve. As I was taking it off I must not have seen it inside the valve. I actually wondered what it was and then I ignored the fact that things should just be hanging there. My bad. After I put the car back together, I tried to fill the tank. I couldn't get more than a squirt in at a time. Managing to get home, I filled the tank from a gas can I had at home albeit very slowly.

Back to reading the Pelican Parts article. The reed switch gets referenced in the comments. Once I saw it and some follow up pictures, I saw my error. I got the car back up on the stands and got the reed switch placed and taped. I was able to then get fuel into the car (although it still has some issues at certain stations). But the howling remained. Whaat?

Back to reading the instructions and comments. Deep in the comments are some threads on blowing out the collection canister.

Lessons learned:

  • Follow the instructions. I'm certain I jumped around and skipped a step with disconnecting the canister.
  • Buy a 10mm nut driver for this job
  • Read the comments to get all the context before taking on the tasks.
  • There's no mention of the reed valve in the article, but there is in the comments...
  • After breaking several plastic rivets I ordered some blue plastic tools for doing this work and some extra rivets

Notes to Self

Got the reed switch in and taped down. Might need to back off the tape and make sure reed valve does its magnetic switch when the gas nozzle is put into tank. It should click. In reading all the comments in the Pelican article and the instructions, I can see that I did not remove both ends of the vent lines and one point in the middle. Let's take those off and gently blow some air through to make sure we don't have any blockages. There's an electrical connection red arrow (figure 2) that we should clip / unclip. Maybe take the whole canister out and inspect it.

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