DaveB

Hi all,
I have a 60k mile MY05 UK F20C powered S2000 that has an intermittent ticking/knocking noise that only appears when warm at idle - it happens for a few seconds then stops then happens again for another few seconds then stops and repeats like this. It disappears when engine revved.
I've adjusted the valve gaps to middle of spec band and replaced pulley bearings but still it's there.
Listen to clip below - the sound is present at the start of the clip then goes then restarts towards the end of the clip:
Any ideas what you think it could be?
Thanks in advance for your wisdom and advice.

NikoS2K

It maybe just my ears but, from what I heard it sounds more like exhaust rattle or a rattle period....maybe catalytic converter?

Car Analogy

I hear some knocking sounds, that coukd be heat shields, etc. Anything from header heat shield to cat shields or cat itself.

But at one point I also hear a high pitched squeal, which sounds like a bearing noise.

Now is the time to do the troubleshooting you didn't do before just changing pulley bearings. Remove or just loosen belt (slip it off tensioner pulley), and see if noise goes away.

Obviously don't run engine long enough to overheat. Issue only happens when warm, so working time greatly reduced since engine already warm when test is done. Also since water not circulating, water temp gauge can't be relied on to be accurate. But you should be able to run for a min which ought to be plenty of time to see of noise still there or not.

If noise is gone, its one of the belt driven items. So check them all. Spin them all by hand. Make sure spin smooth and noise free. Check every pulley (except crank obviously).