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-   -   Exhaust leak? (http://www.bimmerfest.com/forums/showthread.php?t=653230)

tyler3567 10-21-2012 01:26 PM

Exhaust leak?
 
Last week I noticed a little rattle right around 2500rpms, well today that rattle came again for about the 3rd time but shortly changed to what appears to be an exhaust leak. When I got home I lifted it up and it isn't coming from underneath but appears to be coming from the top end. The check engine light hasn't come on and the car appears to be running very normal.

Any thoughts on where to start on this, it might go into my mechanic, but if he doesn't have time I am going to need to get this fixed myself.

Fast Bob 10-21-2012 02:14 PM

You sure that`s not "VANOS Rattle"? That`s right where it normally occurs....does it seem more pronounced as revs are rising, or on the downrev ?

tyler3567 10-21-2012 02:24 PM

Well, I suppose the rattle could be the VANOS. I just had the seals done in the spring, but not the rattle kit, seemed most people said that was a crap shoot on working. The exhaust leak sound appears to be coming from the middle of the engine on the right hand side, which makes me think one of the headers or catalytic converters.

QAfred 10-21-2012 02:27 PM

I had a similar issue, vibration, not a rattle, on the down rev, right around 2000 RPM down to 1800 RPM was the worse. You would have almost thought it was in the drive train it vibrated so much, mainly as I approached 2000 RPM, in 4th or 5th gear, on the down rev only. I also had a slightly rough feeling idle.

I pulled and cleaned the ICV, with carb cleaner, and the vibration went away. Idle smoothed out too.

tyler3567 10-21-2012 03:57 PM

Quote:

Originally Posted by QAfred (Post 7148777)
I had a similar issue, vibration, not a rattle, on the down rev, right around 2000 RPM down to 1800 RPM was the worse. You would have almost thought it was in the drive train it vibrated so much, mainly as I approached 2000 RPM, in 4th or 5th gear, on the down rev only. I also had a slightly rough feeling idle.

I pulled and cleaned the ICV, with carb cleaner, and the vibration went away. Idle smoothed out too.

Hmm, interesting thought, mine is only on the up rev around 2500 rpm, but when I first heard it, it definitely made me think drivetrain. It doesn't always happen, if I come to a stop and start going again it doesn't always come back.

tyler3567 10-21-2012 03:59 PM

Quote:

Originally Posted by Fast Bob (Post 7148759)
You sure that`s not "VANOS Rattle"? That`s right where it normally occurs....does it seem more pronounced as revs are rising, or on the downrev ?

Only as the revs are rising.

QAfred 10-22-2012 05:16 PM

Quote:

Originally Posted by Fast Bob (Post 7148759)
You sure that`s not "VANOS Rattle"? That`s right where it normally occurs....does it seem more pronounced as revs are rising, or on the downrev ?

FB, still curious on the answer to your question. Could you enlighten us?
What could both scenarios be?

More pronounced as revs are rising = ?

More pronounced as revs are on downrev/decreasing = ?

reason I ask is that OP has one issue (rising RPM rattle / noise) I have the other (vibration on downrev at 2000 to 1800).
Cleaning ICV (and MAF/DISA while they were out) cured most of my vibration on the downrev...70%.

tyler3567 10-22-2012 05:33 PM

My mechanic found that a couple of bolts had rusted through and were doing nothing allowing the air to come through and making my noise. This is where the head pipe coming off the engine meets the main pipes going to the back at the flange.

QAfred 10-22-2012 05:39 PM

Thanks for the info! I have something similar going on.

I just put FCAB's on last week, maybe I bumped something down there during removal of the old ones. I remember looking at the 02 sensors and that flange area you speak of, but i think it is time for a total visual inspection before I take anything else apart. ICV needed cleaning anyway- so nothing loss there.

Fast Bob 10-22-2012 05:44 PM

Quote:

Originally Posted by QAfred (Post 7151179)
FB, still curious on the answer to your question. Could you enlighten us?
What could both scenarios be?

More pronounced as revs are rising = ?

More pronounced as revs are on downrev/decreasing = ?

reason I ask is that OP has one issue (rising RPM rattle / noise) I have the other (vibration on downrev at 2000 to 1800).
Cleaning ICV (and MAF/DISA while they were out) cured most of my vibration on the downrev...70%.

From my personal observations, VANOS rattle typically occurs between 1800 and 3000....while still present, it seems to be a little less pronounced when under load (i.e., "on the uprev"). The "marbles in a coffee can" noise seems more pronounced as the revs descend below 3 grand, with less load on the engine.

QAfred 10-22-2012 06:19 PM

okay, thanks for the info. both would be vanos related.

I need to get my head under the hood while my wife is throttling it. To date, I have only revd it with hood upen and did not hear anything. It is all vibration/rough feel in neutral in the 1800 to 2000 rpm range and, while driving you can feel it in the seat of your pants, making me originally think pressure plate/clutch issue (149k and holding out on clutch as long as I can).

Odd I can only feel it in neutral and on downrev while in gear, and smooth as silk all other ways. Getting 29.4 MPG at avg speed of 46mph over the last few weeks of this issue? Actually, a little better than my normal 27.6mpg average but, I attributed mpg increase to new michelin's, RTAB's, FCAB's and alignment...not running lean for some engine issue?


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