Rattling noise under hood

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mvibe2006
Posts: 7
Joined: Sun Oct 12, 2014 1:23 pm

Rattling noise under hood

Post by mvibe2006 »

I own a 2006 Pontiac Vibe which began making a rattling noise a few weeks ago every morning when I start the engine. It only happens in the morning when I leave for work. When I start the engine to go home at the end of the work day, it does not rattle. It sounds like loose ball bearings under the hood, and it only rattles when I’m turning the wheel and/or applying brakes as I back out of my driveway. After a few miles the rattling disappears, so it seems to be related to the engine temperature. After reading another blog thread on this web site, I thought that the rattling noise could be caused by (1) a loose heat shield, (2) the Bendix gear inside the starter, or (3) the VVTI Cam controller. I’ve driven the car onto blocks and crawled under it, but couldn’t find any obvious loose heat shield or panels. The fact that the noise is more pronounced when I’m turning the wheel or applying the brakes makes me skeptical about noise source #2 and #3. Any other suggestions would be greatly appreciated. Otherwise, I’ll just have to take my car to a mechanic and hope that he can solve my problem at a reasonable price.
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Caretaker

Re: Rattling noise under hood

Post by Caretaker »

That's a well constructed note. Yes, you can cross #2 off your list. The failing Denso bendix gear only makes the scratching-metalic sound at startup for 1 second. I would certainly start with #1. Heat shields, especially the one covering the exhaust manifold can make the wackiest noises at the weirdest times. As for #3, I can't comment on when the VVTi timing gear actuator makes the noise. I thought it was only at startup. But what do I and "GM master mechanics" know. They were stupid enough to put in a new one when everyone else under the stars knew the noise I was experiencing was the bendix gear in the starter.
mvibe2006
Posts: 7
Joined: Sun Oct 12, 2014 1:23 pm

Re: Rattling noise under hood

Post by mvibe2006 »

Thanks for your reply. I'll crawl under the vehicle and poke around again to see if I can find anything loose.
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joatmon
Posts: 10018
Joined: Fri Mar 21, 2003 5:19 am
Location: SMC MD

Re: Rattling noise under hood

Post by joatmon »

folks here have described the sound of a worn serpentine belt tensioner as something like "marbles rattling around in a tin can"

Never had it happen in any of mine, can't say if it is something that happens all the time of just on warm up
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