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Discussion Starter #1
Fellas I apologize in advance. I have been all over the forum for months reading and posting, trying to get ideas where to look for this %*^# vacuum leak. Here is a summary:

Getting lean codes. When lightly hitting the gas I hear a loud air hiss whistle squealing noise..definitely an air leak. More throttle it goes away. My fuel trims are perfect at idle but as soon as I touch the gas they drop, but only at light throttle. More gas, the trims go back to normal. Car idles fine, no noticeable power loss, but gas mileage is bad.

I have replaced: CCV, intake boot, DISA seal, throttle body gasket, vacuum lines and caps on the back of the intake, IAC seal, VCG. I have smoked tested it 3 times now and don’t see a thing. Sprayed carb cleaner everywhere I could reach and nothing. Listening at every angle it seems loudest area is up front around the oil filter. Changing the ccv did not do anything so I know it’s not that. What else in that area could cause a leak? Could something inside the DISA be leaking? I hate to pull the intake and replace the gasket if I don’t need to.


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Fellas I apologize in advance. I have been all over the forum for months reading and posting, trying to get ideas where to look for this %*^# vacuum leak. Here is a summary:

Getting lean codes. When lightly hitting the gas I hear a loud air hiss whistle squealing noise..definitely an air leak. More throttle it goes away. My fuel trims are perfect at idle but as soon as I touch the gas they drop, but only at light throttle. More gas, the trims go back to normal. Car idles fine, no noticeable power loss, but gas mileage is bad.

I have replaced: CCV, intake boot, DISA seal, throttle body gasket, vacuum lines and caps on the back of the intake, IAC seal, VCG. I have smoked tested it 3 times now and don’t see a thing. Sprayed carb cleaner everywhere I could reach and nothing. Listening at every angle it seems loudest area is up front around the oil filter. Changing the ccv did not do anything so I know it’s not that. What else in that area could cause a leak? Could something inside the DISA be leaking? I hate to pull the intake and replace the gasket if I don’t need to.


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Did you check the seal on the eccentric motor? My brand New VC leaked from around that one and also at the oil cap.
 

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Discussion Starter #3 (Edited)
No I did not check there. But the sound is coming from the other side around the intake. It is loudest around the oil filter housing, in the direction of the disa/throttle body/ ccv area but i cannot isolate it.
 

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Discussion Starter #4 (Edited)
I should also mention it only happens when the engine is in gear, under a load. No noise when just sitting in park and revving the engine. Frustrating!
 

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Have you ensured the oil filter cap is torqued properly?

Have you replaced the oil fill cap gasket?


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Have you ensured the oil filter cap is torqued properly?

I would hold a lighter around the OF area to check for draw, as that is where you hear the sound.

Have you replaced the oil fill cap gasket?


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Discussion Starter #7
I recently changed the oil and put on a new seal but I’ll recheck the torque. It was doing this before the oil change. I have not checked the filler cap. I will start there. Thanks!


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HDT...this topic is sounding more and more familiar to what Im dealing with. I was hearing a vacuum leak from that same exact area. I couldnt isolate it at all. I did find my disa was shot and I am currently waiting for it to arrive UPS tomorrow. I did the smoke test and found a leak at the eccentric motor and sealed it up real good. Having said this, I never did definitively find that whistle on the left side. I did like you did and checked everything. I am hoping and praying to the car gods that the DISA tomorrow and the sealing around the Eccentric motor does/did the trick. I seen no smoke anywhere during my test and used almost a full can of carb cleaner trying to find the leak and never did. With mine at least, it could be the second DISA on the inside side of the intake....it could also be down below underneath somewhere on that side which scares me. I will find out tomorrow. If I am running the same course as you are,,,,,sounds like I will still be on the hunt. The other thing I wonder is that I know "sound" can be misleading. Sometimes it sounds like it is certainly coming from one area only to find out it was actually from some other place unrelated. Please keep us updated because what you find may end up helping me out quite a bit.
 

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Discussion Starter #9
I definitely will. And please do the same if your have any luck with the DISA. I have read that sometimes the diaphragm on the DISA can leak air and not hold a vacuum and that wont show up on a smoke test. I need to pull mine and see if it does. I did not check for that when I replaced the o ring. I cant think of anything else on that side of the motor that could have a vacuum leak other then the line to the sucking jet pump or the manifold gasket itself. I have replaced everything else!
 

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I decided to break my DISA apart once I knew it wasnt something I wanted to attempt at rebuilding. There are a couple places that the "p*** poor design could leak air. Theres an o ring at the base of the "mast or sail" or whatever you want to call it. The cruddy little seal is what keeps air from entering into the body of it. Common sense says that air could leak anywhere along where the "clamshell" design comes together. However, I seen another point of failure....one not so obvious. On one side of the DISA there is an electrical connection. When you look inside the DISA the connection runs through like a rectangular housing on the inside to a point underneath the circuit board. When I seen that, I realized that was a weak point for air pressure to find its way through. Because of where it is and how tiny it is and the fact that it has to squeeze around a seal and through that housing....I thought just maybe I might not see a noticeable amount of smoke coming out. I will find out soon!
 

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Discussion Starter #12
I didn’t think to check around the purge valve. I wasn’t getting an error code for it so I never even thought of it. I will check it out. Thank you for the suggestion!


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What does the purge valve do?????? Im sure it purges something. Evil BMW spirits?
 

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Discussion Starter #14 (Edited)
Its part of the emissions. It controls the fuel vapors from the tank. I need to check that vacuum line. I may have knocked it loose somewhere..or it may be cracked. I sure hope so! I need something to purge those evil spirits lol
 

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Just throwing this out there...

Are you absolutely sure it***8217;s a vacuum leak? Sure, you get lean codes and trims are varying and all that, but maybe the whistling sound you hear is tensioner or idler pulley telling you the bearing is about done?

My daughter***8217;s X also had whistling noise in the driver***8217;s side front of the engine, but it went away today when I changed both pullies (serpentine belt tensioner and idler) as well as both belts.
 

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Discussion Starter #16
I am 99.9% certain. This is something I have been chasing after for months, both lean codes and this sound. It sure sounds like a vacuum leak. The whistle varies with the throttle. I could almost play a song with the gas pedal.
 

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Discussion Starter #17
Well I dug into it again today. Pulled out the disa, iac, throttle body etc. Disa vacuum was good. Checked out the line on the purge valve. It didnt feel that bad, the rubber on it was still pretty pliable. However feeling the hose connected from the intake to the suction jet pump, it feels really cracked and dry. I wonder if it may have a split in it somewhere. Thinking about it, my brakes have never felt that great. I may be to the point of pulling the intake and replacing all the lines. Probably less work in the long run.
 
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