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F10 M5 (2012 - Current)
The count down is on. The BMW M5 F10 will be released on April 1st, 2011!

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  #1  
Old 04-08-2013, 09:00 AM
droidfan droidfan is offline
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Location: California
 
Join Date: Dec 2012
Posts: 32
Mein Auto: 335IS
Small "knock noise" when passing from 1st to 2nd gear

Hello,

I have noticed a "small knock" noise when passing from the 1st to the 2nd gear in full automatic shifting mode. This noise comes from the middle of the car in the back of the driver on the right hand side.

The car settings are all into "comfort mode" when this is happening and the car was still in "breaking-in period" (meaning before 1250 miles).

Checked with the dealer and made a small test drive with a technician who told me that this was "normal and observable on all M cars - linked to the turbo engaging".

I still consider this as strange as I has not experience this noise on any of the test drive I have done before.

Is there any explanation for this ??

Thx,
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  #2  
Old 04-10-2013, 11:19 PM
BMW BMW is offline
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Location: Ventura County, CA
 
Join Date: Dec 2002
Posts: 6
Mein Auto: M5
It's normal, the overpressure "pop-off" valve opening in the turbo system when the throttle is released for the shift. When the throttle is initially closed the turbos have been providing boost and now it's going into the now closed intake manifold. There is a valve that opens to keep from over pressurizing the intake. In my car it was really noticeable the newer the car was and it gradually lessened as I got close to the 2,000 mile mark on the car. Either that or I just got used to the sound, I hardly notice it any more.
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  #3  
Old 04-19-2013, 11:32 PM
droidfan droidfan is offline
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Location: California
 
Join Date: Dec 2012
Posts: 32
Mein Auto: 335IS
Well, it seems also that I can here this noise between 2nd and 3rd gear.

So this would mean from 1st to 3rd, I would have two knock noise.

Should I consider this normal ??
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  #4  
Old 04-20-2013, 08:32 PM
BMW BMW is offline
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Location: Ventura County, CA
 
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Mein Auto: M5
You may or may not hear the pop-off valve, it depends on the shift speed and the throttle position on each shift. But the sound is normal, I wouldn't worry about it.
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