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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 07-11-2012, 07:03 PM   #1
VABimmerchick
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VANOS, Timing tensioners, or????

I have a 2000 328i with 122k miles. No issues with the car until recently, I began experiencing a very loud rattle. The puzzling thing is that it only makes this noise when the AC is turned on and most of the time it goes away at around 65mph. I've been doing some research on the VANOS issue but also wonder if it could have anything to do with the AC compressor. Any clues??

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Old 07-11-2012, 07:26 PM   #2
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Turning on the A/C wouldn't cause the VANOS to start rattling. If the rattle starts when the A/C starts, it's probably to do with the A/C. If you can get it to happen while it's parked, you can probably isolate where the noise is coming from with a stethoscope. You can buy an automotive version for not too much. Could be an auxiliary fan, too, if the A/C causes that to run.
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Old 07-11-2012, 08:03 PM   #3
VABimmerchick
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Thanks. That may rule out the VANOS....
I thought at first that it might be the aux fan, but that will run at times without turning on the AC and the noise is not there. It will rattle at idle but again, only with the AC turned on. I put it up on ramps and let it idle while I turned on the AC and crawled underneath. It seemed like the noise was coming from the AC compressor. I will take your advice and use a stethoscope to see if my hunch is right.

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Old 07-11-2012, 08:05 PM   #4
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Could be compressor, could be the pulley, could be other things too. AC will introduce a drain which might lower your idle too much if your icv isn't clean...and the rattle could also be the fan, I suppose, which comes on with AC...though it usually goes off when moving.

Also, the AC tensioner could be bad too...can you see if the belt is hopping between pulleys?
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Old 07-11-2012, 08:06 PM   #5
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Turning on the A/C, along with lack of maintenance, can cause extra vibrations giving you the false assumption that it's AC-related. Anything could be loose on your car from exhaust manifold heat shields to pulleys, etc. I'd suggest going over the engine in detail and poking around.
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Old 07-11-2012, 10:49 PM   #6
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Check your exhaust manifold heat shields, just below the SAP. With the engine running, press down on it with a long screwdriver, and see if it stops. Mine did it all the time. I finally dampened the noise with self adhesive heat shield, cut to fit the piece. It makes a horrible sound, and only does it with the AC on. If you want pics, PM me.
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Old 07-12-2012, 12:07 AM   #7
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Originally Posted by MJLavelle View Post
Check your exhaust manifold heat shields, just below the SAP. With the engine running, press down on it with a long screwdriver, and see if it stops. Mine did it all the time. I finally dampened the noise with self adhesive heat shield, cut to fit the piece. It makes a horrible sound, and only does it with the AC on. If you want pics, PM me.

We are talking pics of your custom heat shield right?
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Old 07-12-2012, 12:24 AM   #8
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We are talking pics of your custom heat shield right?
Well, you can stop laughing your a$$ off, because I was talking about pics of the heat shield that is making a rattling noise, not my solution. I wanted to make sure he was clear about the area we were talking about. Not that my solution is anything I am embarrassed about.
Now, if you have a solution that does not involve removing the exhaust manifold to replace the gasket/heat shield, then I would love to hear it. I tried bending it up and down, but it simply refuses to stop vibrating. I have heard it on other e46's as well. Mine vibrated enough to be annoying to me, so I simply dampened the vibration. It works well, and does not interfere with anything else, so I don't see how it would offend anyone's sensibilities.
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