29 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHHumming Noise near gas cap
Reported or suspected cause
valve in the engine compartment
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
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Reported cause
The issue was a valve in the engine compartment that turned vaccine on and off to this check valve the other guy is talking about.
Leading evidence: 'valve in the engine compartment' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'valve in the engine compartment' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check condition of your gas cap seal/gasket' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
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Performed · outcome unconfirmed
Disconnected the throttle body side hose on the valve (thr rubber hose), then slipped a piece of rubber glove over the end of the valve and slid the hose back onto the valve.
Disconnected the throttle body side hose on the valve (thr rubber hose), then slipped a piece of rubber glove over the end of the valve and slid the hose back onto the valve.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
They ran the Porsche super computer against the car.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
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Suggestion
Also a good idea is to check the condition of your gas cap seal/gasket.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed
Disconnected the throttle body side hose on the valve (thr rubber hose), then slipped a piece of rubber glove over the end of the valve and slid the hose back onto the valve.
Disconnected the throttle body side hose on the valve (thr rubber hose), then slipped a piece of rubber glove over the end of the valve and slid the hose back onto the valve.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
29 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
1 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
This engine had a failed AOS that the previous owner didn't fix for a very long time so I'm not suprised this valve got it's share of oil and made it sticky.
New owner of a 2003 cabrio w 36k miles. just got a lot of service done at Rennwerke outside of white plains. They only service Porsches.. Yanked the engine and did new New ims / rms plus full 30k service plus new continentals. The one thing they didn't get to was this weird humming noise emanating near the gas cap. Only hums at idle. When you step on gas pedal it goes away. Owner of Rennwerke said it is likely a faulty check valve tied into the carbon filter / fuel air intake. would require right front wheel well to be opened and some parts replaced. anyone ever experience this problem?
Gas pressure bypass flow back into the pressurized(***) fuel tank when fuel burn is minumum.
Late model cars keep the fuel tank pressurized 24/7, you might hear the pump(***) run even hours post ignition shut down.
On my 99, this was the first symptom of a soon to follow, irratic idle to engine stop then no re-start. The issue was a valve in the engine compartment that turned vaccine on and off to this check valve the other guy is talking about.
Can you please post more on this. I have this "moose" sounding noise coming from the gas cap area when the engine is shut off and if the RPMs drop too low during take off. Also have been chasing a hard start (have to crank it for 10sec or more at times) and my idle is at time incosistemt.
Search "Hard starting after refueling" The regeneration valve is in the engine compartment. Evidently as/when it fails/starts to fail it can "Honk, Squeal, Whistle, Squawk, fly south for the winter..
https://rennlist.com/forums/996-foru...-any-help.html
Pelican has them.
http://www.pelicanparts.com/cgi-bin/...FILTER_TOOL=ON
This does sound like a faulty vent valve also referred to as a bleeder valve. It is located towards the top of the filler neck and is fairly easy to replace. We have new Genuine Porsche vent valves
here
and a write-up about it
here
as well as a quick video about it here:
Porsche 996 Fuel Filler Vent/Bleeder Valve Replacement - YouTube
Yes there is a valve in the engine compartment that turns vaccume and on off to the tank. Mine was sticking open putting a lot of vacc on the tank making it so the pump couldn't pump the fuel.
The valve comes right off the TB and it is mounted right above the plenum rail on the left side. It is about 3" long and has a 2 wire connection. it has a quick connect that attaches it to the hose that runs up to the tank
The one at the filler on my 2004 Mercedes ML 350 quit working, it stayed open. That valve closes when the ECU decides that the conditions are right for a pressure test (Vacuum?) of the vapor recovery system. In that case no electric meant it was open.
If you put your finger over the hole in the grommet under the gas cap I think you will feel vacuum and the "HOOT" will stop as long as you keep your finger there.
I'm pretty sure that the vapor recovery systems work the same.
The valve in the engine compartment pulls fuel vapor into the engine. I cut the Mercedes one open it had a pintle valve (like a fuel injector) that clicks when it is working. When it fails it allows too much fuel vapor into the manifold making mixture too rich for the warm engine. Hence hard starts at hot engine restarts after fuel fill, lots of vapor being pushed around.
The valve under the filler cap closes/seals the system for the integrity test. If it doesn't pull and hold xx inches of vacuum it fails = check engine (PO455 large air leak can also be the gas cap) and /or hooty noises happen.
Put your stethoscope on the one in the engine after things are at operating temp. You should hear it chattering metering fuel vapor from the tank into the manifold. When the ECU calls for test mode engine valve opens to create vacuum, filler vent valve closes to let vacuum build in the tank/charcoal can, lines etc for the vapor recovery system test.
The one in the Mercedes has a light spring that pushed it closed, = no vacuum to pull vapor if it was disconnected. That would stop the hoot noise but if it is the vent valve (gas cap) that is bad, replacing the vapor recovery valve (engine) might not cure CEL or Hoot.
I'm using the Mercedes as an example because it just drove me crazy until I figured out there were two valves that could cause the CEL PO455 I was getting.
Thanks all for your advice. During these posts I had the car back in the shop. They ran the Porsche super computer against the car. And both valves were found to be not operating normally. Both valves (purge and one by vaccuum in engine area) replaced and lines blown out. Was so excited to get car back and not sound like I am driving an overpriced Dyson.... And then that damn sucking sound again
Called back and mechanic said possibly defective gas cap that is not holding the seal. Wish I could get out of this with just a new gas cap. Drama continues.... If I can't fix problem going to reach out to Dyson for sponsorship
Thanks for the pointers, I'll check both valves. I have replaced the gas cap gasket a few weeks ago as it was badly dracked. By the was for future reference, the 996 gas cap gasket is the same as a Dodge Caliber or Neon.
Only the gasket, not the cap.
As Test of the vapour recovery valve. I'll plug it on the gas tank side of the valve and see if the hard start issue resolves. If it does, I'll remove the valve abd see if I can clean it to bring it back to life. If that doesn't work, I'll replace it.
Also a good idea is to check the condition of your gas cap seal/gasket. When it deteriorates, it can cause a vacuum issue as well as a whistling noise. If you take the cap off, you will see the gasket fairly deep inside the cap and you'll be able to see if the surface is smooth or has cracks/tears.
Mark/Pelican Parts
Found and tested the hard start problem. It is the purge valve in the engine compartment, left of the throttle body. Disconnected the throttle body side hose on the valve (thr rubber hose), then slipped a piece of rubber glove over the end of the valve and slid the hose back onto the valve. Did about a dozen engine starts, low RPM take offs and no sign of the hard start or noise from the filler neck area. Next step is to remove the valve and try to clean and bring it back to life.
After plugging the line to the recovery valve pulled the codes and one of them was P0446. So the ECU picked up that the valve was faulty too. I'm away from home so any further work on this will be a few days from now.
Yes, unplugging it while its closed will be a temp fix but will give you a cell. I was also getting a cel pointing to the issue before hand. The cel will go on after a short drive then after pulling up to a light. I foget the code.
[QUOTE=Imo000;10724790]Found and tested the hard start problem. It is the purge valve in the engine compartment, left of the throttle body. Disconnected the throttle body side hose on the valve (thr rubber hose), then slipped a piece of rubber glove over the end of the valve and slid the hose back onto the valve. Did about a dozen engine starts, low RPM take offs and no sign of the hard start or noise from the filler neck area.
Next step is to remove the valve and try to clean and bring it back to life.[/
QUOTE]
Pics if you open it up to clean it.
Took it off and tested it with a 12V cordless drill battery. It was closed and the it openned twice, after that it stuck open. So I poured in some paint thinner and popped the vavle a few times with the battery. Did this from both ends. This seemed to fix it. This engine had a failed AOS that the previous owner didn't fix for a very long time so I'm not suprised this valve got it's share of oil and made it sticky. The valve can not be taken apart to service it.
The one on the engine compartment is connected to the drivers side of the throttle body and sticks out into the area above the alternator. Has electricle connector and vacuum line running through it.
http://www.pelicanparts.com/More_Inf...OEM&SVSVSI=915
