Air whoosh sound on acceleration

[mattg1.8]

I'm having an issue thats slowly been getting worse all week. I just pulled my motor to change the exhaust manifolds and re-installed a couple weeks ago. I switched from the aftermarket tube style manifold to OEM ported manis. Put the motor back in and it ran great. I had an issue with the idle jumping around so I unplugged the MAF and it fixed itself. I got a new MAF and all was good to go. I've been driving it this week and started hearing an air rushing noise coming from passenger side right in front of the firewall. It's lacking power and it wont boost past 10lbs (normally boosting 22). I got underneath and checked the charge side of both turbos for leaks and did a boost leak test and found nothing leaking. I started thinking it may be a wastegate stuck open. I was able to manually move both wastegate arms so I guess that theory is wrong? Could it be a faulty N75 valve? I've seen some other posts about this but no resolution. Any help is appreciated. Thanks.

[Corradovolksb]

Did you pressure test the entire system? You may have a bad check valve at the intake manifold or it could be your throttle body boot.

[mattg1.8]

For the pressure testing I removed the intake and put my homemade 4" PVC piece onto the Y-pipe, I removed the pancake valve and plugged that hole, removed the oil cap, and put 15lbs into the system. I got underneath and could hear the air going through the system but couldn't hear any leaks.

[Bordom]

What did your boost Guage say when you pressurized the system?

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[mattg1.8]

I didn't check, I was too concerned with listening under the hood. Ill have to try again and check it.

[mattg1.8]

could a vacuum line cause this kind of sound and symptoms?

[Corradovolksb]

Yes it can. If it's does not have a check valve or the check valve is bad a broke vacuum line like the brake booster line will leak.

[JustManson]

Not hijacking...

On a boost gauge what would show in this situation? When the motor is on and running what is a typical InHG showing on the guage? If there is a leak would show a different result?



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[QuinnsterKID]

Yes it can. If it's does not have a check valve or the check valve is bad a broke vacuum line like the brake booster line will leak.

Exactly...look at the check valve that plugs into the rubber grommet on the secondary firewall that goes to the brake booster. Mine was whooshing under boost and sounded like it was at my feet while driving. You should be able to blow in it and push out air, but not suck air back in. If you can push and pull air both ways there is your answer.

https://www.europaparts.com/vacuum-c...FUlNfgodEmcDXg

[mattg1.8]

Exactly...look at the check valve that plugs into the rubber grommet on the secondary firewall that goes to the brake booster. Mine was whooshing under boost and sounded like it was at my feet while driving. You should be able to blow in it and push out air, but not suck air back in. If you can push and pull air both ways there is your answer.

https://www.europaparts.com/vacuum-c...FUlNfgodEmcDXg

Is this the one? I just pushed on it and heard air blowing out. The car is off and I was shaking it around a little trying to pull it off the grommet and it kept making an air hissing noise. Is that a good Indication it's bad or do I need to pull the hose off of it to tell?

[slowSfaux]

That's a check valve to keep boost out of your brake booster. Normal to leak air in (it's under vacuum at all times, so you disturbing the fitting actually let air in, not out). If it was bad, you'd have no brake assist anytime you're in boost, and it wouldn't hold vacuum after shutdown.

[Corradovolksb]

The hissing is the vacuum that is stored in the brake booster leaking when you move it causing it to not seal at the grommet. The check valve is good since it's holding vacuum. There are a few other Check valves by the intake that you should check.

[mattg1.8]

I had the engine running and sprayed some stuff down with carb cleaner to try to find some leaks. The green check valve in the first pic under the y pipe made the engine stumble a little when it was sprayed. It wasn't drastic but the rpm changed slightly. What are these two green check valves for and does it make sense that they can be causing this? Also, what is this black vacuum line that's routed behind the abs module? The plastic hose on the inside looks like it was cut and this rubber line was used to replace the broken section.

[mattg1.8]

Can anyone tell me what these hoses belong to? Specifically that one by the abs?

[Corradovolksb]

The hose on drivers side by the abs pump goes to the vacuum reservoir that the engine uses to store vacuum to run mostly the n249. The green valves are for the PVC system.

[YBLEGL]

If the wooshing sound you described is occurring at 10lbs of boost then you should hear the sound when you pressure test it past 10lbs. Clearly it isn't your manifolds because I'm sure you know what a exhaust leak sounds like.

[mattg1.8]

If the wooshing sound you described is occurring at 10lbs of boost then you should hear the sound when you pressure test it past 10lbs. Clearly it isn't your manifolds because I'm sure you know what a exhaust leak sounds like.

Yea it's not exhaust, I just replaced my exhaust manifolds and they were solid. I noticed when I unplug the maf the engine runs almost normal except for the noise. When I plug the maf back in it starts to stumble at low rpms and won't boost correctly. I believe it's a vacuum leak but I cannot find from where. When I pressure test with 15lbs the compressor drops to zero after a couple of seconds. It doesn't sound like it's leaking but how long should it keep the system charged if there's no leaks?

[Corradovolksb]

You sure your throttle body boot is not torn. Your symptoms are pointing that direction. To be 100% sure you should remove it and inspect it. The fact that it runs smooth with the Maf unplugged is pointing toward a leak between the Maf and throttle body.

[AudiTuner1187]

It's your diverter valves, can almost guarantee. Allowing boost pressure to sneak by back into intake vs being forced into engine. Possibly N249 problem but doubt it.

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[YBLEGL]

Like mentioned above remove throttle body boot and inspect, what diverted valves are you running ???

[mattg1.8]

Like mentioned above remove throttle body boot and inspect, what diverted valves are you running ???

I used to have forge but they starting giving me issues so I switched to stock by recommendation of pure motorsports. They were replaced like less than 2k miles ago. Is it possible they're bad again already?

[YBLEGL]

Stock or 710n ???

[mattg1.8]

To be honest I'm not really sure but 710n sounds correct. He said the stage 3 guys run them with no issues normally.

[YBLEGL]

Yea its a 710n then, take off that throttle body boot and inspect.

[vavJETTAw36]

You can unplug and cap the lines going to your DVs with tape even to check the 249. This will keep your DVs from opening. If that doesn't solve it, remove and check DVs


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[mattg1.8]

You can unplug and cap the lines going to your DVs with tape even to check the 249. This will keep your DVs from opening. If that doesn't solve it, remove and check DVs


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Remove the small line on top and put tape over the end of the hose or the nipple on the dv that it came off of?

[AudiTuner1187]

Remove the small line on top and put tape over the end of the hose or the nipple on the dv that it came off of?

You want to cover the lines going back to N249. Leave DVs open to atmosphere.

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[mattg1.8]

Didn't have much time today but I was able to pull the lines off the dv and take it for a ride. Still doing the same thing. I felt all around the throttle body boot and it felt solid I'll pull it off to inspect anyway though. Is a bad dv readily apparent to see when it's removed? What should I look for? Also, is it possible the leak could be coming from the pancake valve off the y-pipe? Mine seems to be on there pretty loose.

[AudiTuner1187]

Didn't have much time today but I was able to pull the lines off the dv and take it for a ride. Still doing the same thing. I felt all around the throttle body boot and it felt solid I'll pull it off to inspect anyway though. Is a bad dv readily apparent to see when it's removed? What should I look for? Also, is it possible the leak could be coming from the pancake valve off the y-pipe? Mine seems to be on there pretty loose.

When you pull it off blow into the side the connects to intake by TBB. If your able to pump it to boost pressure that would be better and see if any air leaks thru. You can also check functionality of piston by putting a mighty vac on where the n249 connects.

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[mattg1.8]

Checked the DV's and throttle body hose. They call check out fine. Checked the hoses going to and from DV as well. no rips or tears. Any other ideas?

[AudiTuner1187]

Checked the DV's and throttle body hose. They call check out fine. Checked the hoses going to and from DV as well. no rips or tears. Any other ideas?

I guess it could be your n75...you can disconnect line from n75 to wastegate and take at ride but do not go wide open throttle, your wastegate will not open and can push some serious boost and blow your car up. I assume u have a boost guage in car? Watch it to see if you can get boost above 10 psi with line disconnected. If so, then there lies your problem.

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[616_S4]

Where does the sound come from when in the car?


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