Need help, trying to diagnose cause of this rattling sound

GregBelleville · Sep 29, 2023

I'm getting this rattle upon cold startup, it goes away as the engine warms, but you'll hear in the video that it comes back when I rev engine to higher rpms.

To me it sounds like it's coming possibly from a pulley near the power steering pump or somewhere in that area, maybe an idler pulley?

Anyone heard a similar noise or have any ideas what this could be?

billyp · Sep 29, 2023

I would check the bolts from the exhaust manifold to the cats. Mine were pretty loose.

GregBelleville · Sep 30, 2023

Are you talking about these bolts where the exhaust manifold connects to the head?

AndyG · Sep 30, 2023

I’d check the 4 precat bolts and also watch the water pump- Sometimes if it’s a bearing you can use a little water or WD-40 on it to quiet down temporarily and isolate the problem

billyp · Sep 30, 2023

Not the ones at the head, the ones to the precats (couldn’t remember what they were called last night). Basically the other end of the manifold you have in the pic.

GregBelleville · Sep 30, 2023

billyp said:
Not the ones at the head, the ones to the precats (couldn’t remember what they were called last night). Basically the other end of the manifold you have in the pic.

So you're saying the bolts at the flange to the exhaust pipe?

GregBelleville · Sep 30, 2023

AndyG said:
I’d check the 4 precat bolts and also watch the water pump- Sometimes if it’s a bearing you can use a little water or WD-40 on it to quiet down temporarily and isolate the problem

Sorry I'm trying to understand where you're referring to for the 4 pre cat bolts, can you point it out in this diagram?

billyp · Sep 30, 2023

Correct at the flange. On your diagram, the flange where it says “Seal Ring”. Sorry my 2005 is a little different. There are 2 pre catalytic converters right after the exhaust manifold. Looks like the 99 only has a single flange. I would check those bolts. I had those loosen up on a few cars.

GregBelleville · Sep 30, 2023

billyp said:
Correct at the flange. On your diagram, the flange where it says “Seal Ring”. Sorry my 2005 is a little different. There are 2 pre catalytic converters right after the exhaust manifold. Looks like the 99 only has a single flange. I would check those bolts. I had those loosen up on a few cars.

Ok I'll give that a look, it really sounds like a worn out bearing to my untrained ear, just trying to narrow it down to a likely suspect.

AndyG · Sep 30, 2023

GregBelleville said:
Sorry I'm trying to understand where you're referring to for the 4 pre cat bolts, can you point it out in this diagram?

View attachment 461750

They are going to be a here- I think they are 14 or 15 mm and you will usually best reach them from underneath directly above the front driveshaft-

AndyG · Sep 30, 2023

Greg, a swivel head socket and a few extensions is handy-

Some autos get a rattle at the bellhousing, just Fyi.

Keep after it.

GregBelleville · Sep 30, 2023

AndyG said:
Greg, a swivel head socket and a few extensions is handy-

Some autos get a rattle at the bellhousing, just Fyi.

Keep after it.

Will do, thanks for the tips. Just ordered an automotive stethoscope to try and help me track it down.

GregBelleville · Sep 30, 2023

Well I tightened down the exhaust flange as suggested and also replaced the idler pulley. Fired her up and no more rattle. We'll see if it stays gone, but my suspicion was a worn idler pulley, as that was the area the sound seemed to be coming from.

AndyG · Sep 30, 2023

GregBelleville said:
Well I tightened down the exhaust flange as suggested and also replaced the idler pulley. Fired her up and no more rattle. We'll see if it stays gone, but my suspicion was a worn idler pulley, as that was the area the sound seemed to be coming from.

I think you got it too- it sure sounded like it.

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Need help, trying to diagnose cause of this rattling sound

GregBelleville

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billyp

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GregBelleville

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AndyG

Because some other guys are perverts

billyp

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GregBelleville

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GregBelleville

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billyp

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GregBelleville

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AndyG

Because some other guys are perverts

AndyG

Because some other guys are perverts

GregBelleville

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GregBelleville

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AndyG

Because some other guys are perverts

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