Loud knocking from Alternator

Sparky68 · 11-06-2014, 02:06 PM

Bearing gone? Easy fix?

Just pulled onto the drive and noticed a metallic knocking noise that would rise and fall with engine revs.

Anyone know if its a DIY?

Cheers

afalton · 11-06-2014, 03:58 PM

Could be depending on how you feel your skills and toolkit like. Get a long screwdriver with a hard plastic handle with the engine running get the screwdriver on the alternator and put your ear on handle and have a mate rev the car as it could be a different pulley.
Good luck

Sparky68 · 11-07-2014, 10:14 AM

I think it is the alternator. I remember the car making a low grinding noise when I pulled into work in the morning but put it down to brakes or something.

The knocking is very noticeable around the alternator area and have ordered one to replace it. Will check everything else while its apart though.
Anything else in the area I should pay attention to specifically ?

kulfon · 11-07-2014, 10:53 AM

The A/C compressor?

Sparky68 · 11-07-2014, 06:35 PM

Hopefully not, hardly use aircon and was not active when the noise first manifested itself.

kulfon · 11-08-2014, 07:53 AM

It does not have to be on. I had a knocking noise coming out for the compressor even if the A/C was not switched on - problem with the bearing and I ended up with a new compressor (warranty covered it). It is easy to check - just remove the auxilary belt that is connected to it and switch the engine on for a moment.

11-06-2014, 02:06 PM	#1
Sparky68 Brigadier General 798 Rep 4,360 Posts Drives: 2016 M2 Alpine White Join Date: Oct 2012 Location: Cambs UK iTrader: (11) Garage List 2016 BMW M2 [0.50] 2017 BMW F30 330D [0.00] 2014 M135 [0.00] 2007 BMW 335i [0.00]	Loud knocking from Alternator Bearing gone? Easy fix? Just pulled onto the drive and noticed a metallic knocking noise that would rise and fall with engine revs. Anyone know if its a DIY? Cheers __________________ OG M2 7sp DCT Masata FMIC -Masata Boost Pipe - Cobra Catless DP - Powervalve Exhaust - Devilsown Methanol Injection Turbosmart BOV BM3 Stage 3 Halim custom map Pure 500
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11-06-2014, 03:58 PM	#2
afalton Lieutenant 11 Rep 442 Posts Drives: bmw e92 330i m sport Join Date: Oct 2012 Location: london iTrader: (2)	Could be depending on how you feel your skills and toolkit like. Get a long screwdriver with a hard plastic handle with the engine running get the screwdriver on the alternator and put your ear on handle and have a mate rev the car as it could be a different pulley. Good luck
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11-07-2014, 10:14 AM	#3
Sparky68 Brigadier General 798 Rep 4,360 Posts Drives: 2016 M2 Alpine White Join Date: Oct 2012 Location: Cambs UK iTrader: (11) Garage List 2016 BMW M2 [0.50] 2017 BMW F30 330D [0.00] 2014 M135 [0.00] 2007 BMW 335i [0.00]	I think it is the alternator. I remember the car making a low grinding noise when I pulled into work in the morning but put it down to brakes or something. The knocking is very noticeable around the alternator area and have ordered one to replace it. Will check everything else while its apart though. Anything else in the area I should pay attention to specifically ? __________________ OG M2 7sp DCT Masata FMIC -Masata Boost Pipe - Cobra Catless DP - Powervalve Exhaust - Devilsown Methanol Injection Turbosmart BOV BM3 Stage 3 Halim custom map Pure 500
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11-07-2014, 10:53 AM	#4
kulfon New Member 2 Rep 13 Posts Drives: E90 330i Join Date: May 2014 Location: Edinburgh iTrader: (0)	The A/C compressor?
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11-07-2014, 06:35 PM	#5
Sparky68 Brigadier General 798 Rep 4,360 Posts Drives: 2016 M2 Alpine White Join Date: Oct 2012 Location: Cambs UK iTrader: (11) Garage List 2016 BMW M2 [0.50] 2017 BMW F30 330D [0.00] 2014 M135 [0.00] 2007 BMW 335i [0.00]	Hopefully not, hardly use aircon and was not active when the noise first manifested itself. __________________ OG M2 7sp DCT Masata FMIC -Masata Boost Pipe - Cobra Catless DP - Powervalve Exhaust - Devilsown Methanol Injection Turbosmart BOV BM3 Stage 3 Halim custom map Pure 500
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11-08-2014, 07:53 AM	#6
kulfon New Member 2 Rep 13 Posts Drives: E90 330i Join Date: May 2014 Location: Edinburgh iTrader: (0)	It does not have to be on. I had a knocking noise coming out for the compressor even if the A/C was not switched on - problem with the bearing and I ended up with a new compressor (warranty covered it). It is easy to check - just remove the auxilary belt that is connected to it and switch the engine on for a moment.
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