Howling Noise From Fuel Cap Area: Replacing the Carbon Control Valve - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Vehicle: 2000 986 Base, 2.7L Problem: Howling/whistling noise from fuel filler area while driving Difficulty: Really easy, because I was able to do it. The 986 has a system to capture and prevent fuel tank fumes from escaping into the environment. The EVAP system consists of a series of vacuum lines and valves along with a carbon canister that stores the fumes until they can be burned in the engine. The major components of the system can be found in the passenger side wheel well/fender area. Failure of the components of the system can lead to a CEL, or can cause difficulty filling the tank with fuel. One of the more common issues caused by a problem with this system is the infamous "whistle" that emanates from the fuel filler door/fender area while driving. In some cases, the noise sounds like someone blowing across the top of a soda bottle. My 2000 base developed this whistle recently. My research indicated that a number of component failures can cause the whistle. A bad gasket in the gas cap is the easiest and cheapest fix. Another common cause of the whistle is the Fuel Tank Vent Valve (p/n 996-201-143-01, currently $124 from Pelican) which is mounted on the filler tube. Pelican has an excellent video on replacing the Fuel Tank Vent Valve here: https://www.youtube.com/watch?v=zulI06TPBVc . In my case, whatever malfunction I was experiencing with this system was not throwing a CEL, which might have made diagnosis a bit easier. I decided that the only real choice I had was to use the process of elimination to see if I could silence the coke-bottle-whistle. I started by replacing the fuel cap. That was a fail. So I replaced the fuel tank vent valve. Same result. After some research here and other forums, I decided to replace the Carbon Control Valve (p/n 996-605-213-01). This valve is located inside the passenger side fender behind the headlight assembly. It is mounted in a plastic valve housing side-by-side with another valve in the system: p/n 996-605-201-01. I decided to replace both valves while I was in there. Parts Required: Carbon Control Valve: P/N 996-605-213-01 ($108 via Pelican) Purge Valve Fuel Vapor Canister (optional, if you decide to replace both valves): P/N 996-605-201-01 ($85 via Pelican) Tools Required: T25 Torx bit. Recommended: ¼ in ratchet with 3 in extension. Also recommended: trained chimpanzee. Space is tight in the fender! Begin by removing the passenger side headlight assembly. As you shine a flashlight up into the fender, you’ll see the valve housing and the two valves. (Note: I had removed the wheel well liner for another project) The two valves are mounted side-by-side. You’ll need to remove the valve nearest you, P/N 996-605-201-01, to get to the other valve. Both valves are different sizes and have different electrical connections, so you can’t mix them up. The first valve has a metal clip. Pry it out gently then the connector pulls off relatively easy. This will give you a bit of extra space to get to the torx screw that holds the plastic retainer. You’ll need to remove this screw to slide up the retainer and remove the valves. The valve is very snug in the housing, thanks to a hard rubber o-ring. I used a soft plastic trim removal tool to gently pry out the valve. You can now get to the second valve, P/N 996-605-213-01. The electrical clip is different, and it will be much easier to disconnect it once you have the valve out of the housing. Again, I used my trim tool to separate the valve from the housing. To remove the connector, you’ll gently pry the plastic tabs and pull it off of the valve. Now comes the fun part: installing the new valve. It’s a very, very tight fight, and you have virtually no room in the fender to gain any leverage. I found that if you push down as hard as you can, while wiggling the valve back and forth, it will eventually pop in. Swearing and loud grunting noises seemed to help. Make sure you reconnect the electrical to the back valve before installing the front valve. Once the valves are back in, refasten the plastic retainer with the torx screw, then reconnect electrical to the front valve, and you’re done. I confirmed the blowing-bottle noise was gone on my test drive, but I haven’t cracked open the champagne yet. The noise was intermittent before, so I won’t be confident I fixed the issue until I’ve driven some more. Thanks to our wonderful New England weather right now, that might be awhile. Note: there is yet another 996-605-201-01 purge valve on the carbon canister itself. I'll have to take a look at that one if the problem isn't solved. Also, my understanding is that a clog in any of the associated lines can cause an issue as well. this is certainly a complex system with multiple modes of failure. I sure hope this fixed my problem...

Hello, Thanks for posting this info! The same howling noises started this week on my 2000 2.7L. Did the your repairs fix the problem? thanks so much Mike

I did this fix on my car this evening--replacing the fuel tank vapor control valve to get rid of what has been described as the "blowing over a bottle" noise, the "train whistle," or the "howling noise from the gas cap area." I replaced the same part as the OP--P/N 996.605.213.01--and it seems to have solved the problem for me. Based on the OP's DIY instructions above, though, I suspect I had a much easier time completing this project, for five reasons. First, you definitely want to remove the fender liner. Doing so gives you the ability to reach around under the fender with your left hand while you're pulling the solenoid out (or pushing it back in) through the headlight opening with your right hand. Second, remove the two 12mm (?) bolts that hold the bracket for the solenoids to the body of the car. That allows you to drop the whole assembly down a few inches and gives you additional room to pull out the old solenoid and push in the new one. It also gives you room to fit a full-size hex screwdriver in there to remove the hex screw that holds the bracket for the solenoids in place. Third, by doing the step above, I eliminated the need to remove the solenoid that I WAS NOT replacing. For that solenoid, I left it in place and just removed its electrical connection. Fourth, I added a little water-based lubricant to the O-rings on the new solenoid to help it slide in easier. And fifth, and most important, I noted that the solenoid has an index protrusion, which means it only fits in one way. (You can see it at the bottom of the white part of the solenoid in the last photo above.) I suspect that the OP wasn't getting the protrusion lined up properly with the slot in the opening that the solenoid fits into, which is why the new solenoid wasn't going in easily for him. I didn't have much difficulty at all getting it pushed into place once I figured that out. All in all, the actual solenoid replacement took maybe 10 minutes, total, once I got the fender liner out and removed the headlight assembly. A big thanks to the OP for tackling this project and making this DIY. Hopefully my additions here will make the project go even more smoothly for the next person who follows the DIY. (Especially if, like me, they don't have a trained chimpanzee. )

Hi guys, 2001 986 2.7 Boxster base, California car. 125,000 miles. No drivability problems noticed. I wanted to add my experience to this thread to try to help someone out in the future. My sons car was having a few issues at the same time and that added a bit of hesitation to my diagnosis (throwing darts) of the problem. He had both bank 1 & 2 giving "Cat efficiency" codes, a P0445 Shutoff valve, activated charcoal filter and the very obvious coke bottle whistling noise at the fuel fuller flap. The cat efficiency faults were fixed by installing brand new cats after the first set of used (apparently fine) cats didn't change anything. The P0445 first got the very commonly suggested fuel tank vapor valve replaced (after blowing air through all hoses / pipes) purchased from Pelican parts. After installing this wrong and having gas spit out on me when trying to fill because i didn't place the tiny cylindrical magnet back into the correct place, i took it out again, reinstalled it and still had the noise & code. Next was the purge valve in the engine bay under the intake - no change. Next up was the charcoal cannister - i considered a used one but decided to go with pelican again and $350 later - same condition. I knew i couldn't throw this car away over a check engine light so i continued on. And before anyone says that i should be 'testing' these components before just throwing cash away... intermittent failure / passing of tests is a thing and I'm not sure what a good reading / signal / flow should look like. I decided to try a used (perfectly fine I'm told) F & G valve set pictured above and they came with hoses D & C - no change. Same result. I'm now telling myself I've replaced every component in the fuel vapor recovery system and I'm frustrated and $1000 poorer. Yes, any normal person would have taken it to a shop and allowed them to guess with my cash instead. We were coming up on a smog check and the MIL needed to be turned off and the only part that was replaced with a used one was the F & G valves - So Pelican kindly sold me 2 new ones and finally the code was cleared. My son says that he sometimes hears the coke bottle noise but i haven't heard it. I'm just happy the light is out and hasn't returned in over 500 miles,