Rattling sound during cold start up

tilua · 01-14-2019, 04:11 PM

I haven't been running my car for the last couple months due to multiple issues (radiator leak, DME, coil, etc). However, I finally got the car back up and running and for some reason I get this rattling sound from the serpentine belt area during cold start up. It would go away after a few minutes once the engine warms up. I dont' think it's the belt as the rattling is intermittent and also the belt was just replaced less then 10K miles ago. Any ideas?

here's the video

https://www.youtube.com/watch?v=hb8M3cfR01I

KnobDE · 01-17-2019, 06:16 AM

I would really try to take of the belt and listen if sound is still present, sounds like something is kinda stuck

dpaul · 01-17-2019, 06:33 AM

OP - I agree it's not going to be the belt itself but possibly a bearing on one of the pulleys or accessories.

KnobDE's suggestion to remove belt and see if noise is still present seems like a good one and easy to implement if you've got an T60 torx bit and nice long 1/2" breaker bar. I remove the radiator fan to get access (one T20 torx screw and one plastic clip to depress on the side opposite the screw).

Obviously you'll lose power steering, A/C and alternator function and get some warning lights but you're not driving anywhere, just listening for noise at idle, so it should not be an issue.

Other potential explanations (that I consider less likely) are timing chain rattle related to the tensioner sticking or VANOS issues to reduced or irregular oil flow. There's a VANOS oil supply filter that screws into the cylinder head that can become clogged. It is rarely discussed on this forum but easy enough to remove and clean/check. I've seen this happen without throwing any codes.

01-14-2019, 04:11 PM	#1
tilua Private 19 Rep 97 Posts Drives: 2008 335i convertible Join Date: Oct 2011 Location: Houston iTrader: (0)	Rattling sound during cold start up I haven't been running my car for the last couple months due to multiple issues (radiator leak, DME, coil, etc). However, I finally got the car back up and running and for some reason I get this rattling sound from the serpentine belt area during cold start up. It would go away after a few minutes once the engine warms up. I dont' think it's the belt as the rattling is intermittent and also the belt was just replaced less then 10K miles ago. Any ideas? here's the video https://www.youtube.com/watch?v=hb8M3cfR01I
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01-17-2019, 06:16 AM	#2
KnobDE New Member 0 Rep 12 Posts Drives: E92 335i Join Date: Jul 2017 Location: Germany iTrader: (0)	I would really try to take of the belt and listen if sound is still present, sounds like something is kinda stuck
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01-17-2019, 06:33 AM	#3
dpaul Lieutenant Colonel 654 Rep 1,893 Posts Drives: 2009 E90 335xi, 2011 E93 M3 Join Date: Dec 2012 Location: Boston iTrader: (3)	OP - I agree it's not going to be the belt itself but possibly a bearing on one of the pulleys or accessories. KnobDE's suggestion to remove belt and see if noise is still present seems like a good one and easy to implement if you've got an T60 torx bit and nice long 1/2" breaker bar. I remove the radiator fan to get access (one T20 torx screw and one plastic clip to depress on the side opposite the screw). Obviously you'll lose power steering, A/C and alternator function and get some warning lights but you're not driving anywhere, just listening for noise at idle, so it should not be an issue. Other potential explanations (that I consider less likely) are timing chain rattle related to the tensioner sticking or VANOS issues to reduced or irregular oil flow. There's a VANOS oil supply filter that screws into the cylinder head that can become clogged. It is rarely discussed on this forum but easy enough to remove and clean/check. I've seen this happen without throwing any codes.
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