Snap Oversteer

Hi folks, I'm trying to solve an annoying issue and would appreciate any advice you can provide.
Vehicle is a 2000 986 base 2.7L.
Issue: the infamous intermittent noise coming from the fuel filler area that sounds like someone blowing over the top of a soda bottle. No CEL. Car is not hard to start. No refueling issues. Does not correlate to any particular RPM or throttle position. The noise begins a few minutes after startup and continues intermittently.
I've done multiple searches on this forum and several others. Here's what I've done so far to try to stop the noise.
Replaced the Regeneration Valve on top of the engine intake manifold (996 110 129 06).
Replaced both valves in the passenger side fender area behind the headlight (996 605 213 01 and 996 605 201 01).
I have yet to try replacing the valve on the fuel filler neck -- I'm reluctant to do so as I have no issues refueling. I'm considering replacing the valve in the carbon canister (996 605 201 01). If you folks have any good ideas, I would appreciate hearing them before I start throwing more money at parts. Thanks!


Kevin

Macster

Not clear from your post but if you only hear the noise when the car is underway be sure the front trunk lid is secure and latched. Be sure the leading edge of the front trunk lid is *below* the trailing edge of the front bumper cover. If the trunk lid is even just flush this can create a noise as the car moves down the road.

If the noise is present when the car is stationary the cause can be from item #8 in the parts drawing and parts list at the link below:

http://www.autoatlanta.com/porsche-p...section=201-20

Before you throw big money at the problem be sure the cap is ok. My 2002 Boxster gas cap tether broke (at around 300K miles) but the cap rubber seal was quite bad and I'm surprised it didn't leak.

Up to you but you could try replacing the gas cap before you do anything else.

Snap Oversteer

Thanks Macster. I failed to note that I did indeed replace the gas cap.
I was wondering about the valve housing -- the price makes me a little weak in the knees.
The noise does not seem to be present when the car is stationary. It seems to start after driving for a couple of minutes. My hunch is that a valve somewhere in the system tries to close during the purge phase and doesn't seat properly, but that's just a guess. This is a very complex system, and I must confess I don't understand it all that well.

Macster

You are right the system is complex and I don't claim to be an expert. The part is expensive and while it may be needed one wants to be sure.

Have you checked for any pending error codes? An error code, even a pending one, might shed some light on what component could be causing the problem.

Snap Oversteer

No pending codes...one of those rare times where I was actually hoping for a CEL.I have a bad feeling this is something very insidious. I found a thread over on RennTech -- poor guy had been trying to solve his issue for weeks. He finally gave up and took it into the dealership. They eventually found that the valve on the filler neck had a tiny hairline crack.

Macster

Only thing worse than having the car manifest a symptom or symptoms and a CEL is having the car manifest a symptom or symptoms without a CEL.

Have to believe that the fact you hear a noise and frequently and yet there is no active error code (with a CEL) or a pending error code would to a qualified tech provide him with a clue as to what's wrong. Also, if the tech has good experience he's had to encounter this before and probably has a good idea of what's wrong.

I re-read your first post and note you have replaced a fair number of parts. You balk at replacing the valve on the fuel filter neck.

You might reconsider replacing that valve. In for a penny, in for a pound...