* Skip to second paragraph for details on the noise * Hi all.
My other half's nephew left for the Philippines for a vacay, and asked that I look into a noise that has developed recently in his Corolla. This forum has helped me numerous times so I've started to get a little embarrassed to post my next q here, so ( instead of googling for hours ) I've started to solve my problems through trial and error. I've learned a lot during this time, but I'm still prone to error, which - due to the car not being my own - makes me reluctant to take this engine apart and zero in on the source of the noise.

The noise is hard to describe - I would say it sounds like a marble bouncing around inside of the engine block - not a heat shield rattle nor a worn water pump bearing sound, but a deep rapping noise on metal. Also the knocking is brief - no longer than five seconds or so - and intermittent, occurring only immediately after ignition and AFTER acceleration. It seems to be coming from the crankcase area, on the crank pulley side of the motor, but I haven't put the car on stands yet so I can't be sure... I'm sure it's not the water pump ( noise would be constant ), the heat shield and intake, but that's all Google gave me on terms of an answer... Thank you in advance!

Also, if there is a way to upload video, let me know. That would help answer any other questions you all might have.

Update : Finally found the time to get under the hood again. It seems I was totally off in my assumption that it was the belt and the noise is definitely not metal-hitting-metal... I pinned the origin of the sound to coming from either inside or directly underneath the plastic intake manifold. I think there might be a loose tube??? I worked on a gm3800 with the plastic intake and found the source of a blown head gasket to be a narrow coolant tube that ran through the intake and into the head... Similar design? It doesn't run overly hot, so maybe some other plastic piece inside?

  • auto or manual? if you want to post a video just link wherever you upload it. try to localize the noise as much as possible. what's the service history like? frequent oil changes? has the timing belt ever been done? does it still make noise with the serpentine belt removed? how are the fluid levels? is the engine oil low? check engine light on?
    – Ben
    Jun 3, 2017 at 2:24
  • Thanks for the reply! I suspected the belt, but will starting it without the belt have any negative consequences? Also fluid levels nominal, no check engine light, and I'll call my nephew to get the last check up date. Jun 3, 2017 at 2:32
  • just don't kill the battery running the engine without the belt on. it'll be pretty obvious if it's an accessory or not with the belt removed. it also wouldn't hurt to do a visual inspection of the mounts etc...
    – Ben
    Jun 3, 2017 at 2:34

1 Answer 1


Turns out there is a billion out on this problem. I don't wanna play links but it's there. Inside of the intake there is a baffle that comes loose and creates this noise.

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