Rattling sound at idle when AC switches on

E90Company · 07-13-2012, 07:44 PM

Hello,

I noticed a rattling sound at idle if my AC is switched on. If it is off, there is no sound at all. At first I thought it could be wastegate rattle, but I am idling, and when I rev it there is no rattle. Is this normal?

Thanks,
E90

The sound is almost like someone placed a quarter on a running engine and it is bouncing around, very faint.

Duke · 07-14-2012, 12:22 PM

Yeah mine has the same noise after I drive around for a while and come to a complete stop. With or without the A/C on it makes the "tin can full of change" rattling noise. Rev it a little and the noise goes away, then when it hits idle for a couple of seconds the noise returns. After a minute at idle the noise slowly slowly starts to fade and eventually ceases.

J

scottp999 · 07-14-2012, 12:27 PM

Forge diverter valves? Mine had a little too long of hose (maybe by 1mm) and under the right conditions the diverter valves would touch and it would rattle. From inside the car it was hard to tell where it was coming from and I initially thought downpipes were rubbing, but it was just the diverter valves.

Blubaron79 · 07-14-2012, 01:36 PM

Mine kind of has a fluttering sound when you have the AC on. You can hear it when you come to a stop.

E90Company · 07-14-2012, 02:10 PM

Sounds like it's a normal thing then. Thanks.

Duke · 07-16-2012, 06:14 PM

does it sound like this?

<iframe width="480" height="360" src="http://www.youtube.com/embed/wF9N-R_PBFQ" frameborder="0" allowfullscreen></iframe>

E90Company · 07-16-2012, 06:16 PM

Quote:

Originally Posted by Duke

does it sound like this?

<iframe width="420" height="315" src="http://www.youtube.com/embed/wF9N-R_PBFQ" frameborder="0" allowfullscreen></iframe>

Very similar if not the same. Do you have any info about it?

Duke · 07-16-2012, 06:23 PM

just that it sounds like poop lol.

E90Company · 07-16-2012, 06:30 PM

Quote:

Originally Posted by Duke

just that it sounds like poop lol.

I know

Jay1101 · 06-22-2021, 09:52 PM

Really old thread but has anyone found the reason for this?

Saif2018 · 06-23-2021, 12:15 AM

If it comes on when AC is on, It could be blower motor/fan rattle. Have a search on YouTube or Google for fix.

07-13-2012, 07:44 PM	#1
E90Company Major General 194 Rep 6,136 Posts Drives: Car Join Date: Mar 2012 Location: FL iTrader: (2)	Rattling sound at idle when AC switches on Hello, I noticed a rattling sound at idle if my AC is switched on. If it is off, there is no sound at all. At first I thought it could be wastegate rattle, but I am idling, and when I rev it there is no rattle. Is this normal? Thanks, E90 The sound is almost like someone placed a quarter on a running engine and it is bouncing around, very faint. Last edited by E90Company; 07-13-2012 at 07:50 PM..
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07-14-2012, 12:22 PM	#2
Duke Lieutenant 16 Rep 510 Posts Drives: E92 335i Join Date: Feb 2008 Location: The Hills next to CHINO iTrader: (1)	Yeah mine has the same noise after I drive around for a while and come to a complete stop. With or without the A/C on it makes the "tin can full of change" rattling noise. Rev it a little and the noise goes away, then when it hits idle for a couple of seconds the noise returns. After a minute at idle the noise slowly slowly starts to fade and eventually ceases. J
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07-14-2012, 12:27 PM	#3
scottp999 Brigadier General 133 Rep 4,764 Posts Drives: 4runner SR5 Join Date: Mar 2007 Location: MD iTrader: (2) Garage List 2007 BMW 335 [9.00]	Forge diverter valves? Mine had a little too long of hose (maybe by 1mm) and under the right conditions the diverter valves would touch and it would rattle. From inside the car it was hard to tell where it was coming from and I initially thought downpipes were rubbing, but it was just the diverter valves.
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07-14-2012, 01:36 PM	#4
Blubaron79 Brigadier General 1432 Rep 4,724 Posts Drives: 2021 M340i xDrive Join Date: May 2009 Location: PA iTrader: (0)	Mine kind of has a fluttering sound when you have the AC on. You can hear it when you come to a stop. __________________ Current: 2021 M340i xDrive Previous: '18 340i xDrive; '15 335 xDrive; '14 435i xDrive; '09 335 E92 xDrive
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07-14-2012, 02:10 PM	#5
E90Company Major General 194 Rep 6,136 Posts Drives: Car Join Date: Mar 2012 Location: FL iTrader: (2)	Sounds like it's a normal thing then. Thanks.
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07-16-2012, 06:14 PM	#6
Duke Lieutenant 16 Rep 510 Posts Drives: E92 335i Join Date: Feb 2008 Location: The Hills next to CHINO iTrader: (1)	does it sound like this? <iframe width="480" height="360" src="http://www.youtube.com/embed/wF9N-R_PBFQ" frameborder="0" allowfullscreen></iframe>
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07-16-2012, 06:23 PM	#8
Duke Lieutenant 16 Rep 510 Posts Drives: E92 335i Join Date: Feb 2008 Location: The Hills next to CHINO iTrader: (1)	just that it sounds like poop lol.
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06-22-2021, 09:52 PM	#10
Jay1101 New Member 0 Rep 13 Posts Drives: 2007 335i Join Date: Dec 2020 Location: Rockville, MD iTrader: (0)	Really old thread but has anyone found the reason for this?
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06-23-2021, 12:15 AM	#11
Saif2018 Brigadier General 973 Rep 3,219 Posts Drives: E90 335i Join Date: Jan 2019 Location: UK iTrader: (0)	If it comes on when AC is on, It could be blower motor/fan rattle. Have a search on YouTube or Google for fix. Last edited by Saif2018; 06-23-2021 at 12:24 AM..
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