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Catalytic Converter "Rattles"

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I recently had my 2000 Boxster S in for rear brakes, exhaust and power steering service (none of which i was comfortable doing at the time, thought that has changed now). On the invoice, the technician noted that the nearside (driver's side, which is on the right for my car) catalytic converter "rattles." I know exactly what he's talking about; I hear this weird vibration when the car is at low speeds and idle, and it bothers me.

Is there a shield of some sort that might be rattling? If not, do I need to replace the catalytic converter to stop this weird vibration/rattling noise? I'm really hoping I can avoid replacing it...they're not cheap.


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There are heat shields which are known to rattle in the O sensor area and above the cat, the cat. self can rattle as well.You will look closely to see precisely what's happen.

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Another source of the 'rattle' and sometimes put down to the heat shields is the parking brake cable being loose. This causes the brake shoes to rattle when passing over bumps at low speeds. It's very simple to confirm and fix; To confirm drive slowly over bumps and pull up the hand brake lever by a very small amount (not enough to engage the ratchet. If the rattle disappears it is the cable. To fix; the adjuster is under the tray in the centre console storage box. Park on a flat surface, release the parking brake; The are two nuts, one being a lock nut, release that; now adjust the cable so that the slack in the cable is just removed. The handbrake should still be able to be pulled up 3 clicks. Re-tighten the lock nut. The car should still moved when pushed on a single click

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  • 2 weeks later...

I had a rattle as you described on my 2000 Boxster S and after ruling out any external heat shields I ended up replacing the catalytic converter/header on the passenger side. I cut open the older cat to see what was causing the rattle and it turns out that there are a set of thin gauge steel 'cans' that the actual catalyst material is encased in within the actual converter case. These thin cans are spot welded and eventually those spot welds can fail due to repeated thermal cycling and cause the can pieces to rattle against each other when the cat heats up. Its a super annoying noise and your only options are to replace the whole (expensive) part or to try and cut one open and tack it back together if you are good with a welder. I was able to manage to do this but I had already installed my new header, but I can at tell you that it is possible to do. I recommend not buying a used one cause it may end up doing the same thing eventually. Good luck!

Edited by oguralp
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  • 3 months later...

Today I will be trying the adjustment of the hand brake, as when I got the car back from the dealership after the rear brakes were replaced, the sound had gone. It doesn't make the rattling going over bumps, though.

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