Spyder Help diagnosing intermittent knocking sound issue

[jb705]

Hello all,

99 spyder (4g64 SOHC). I replaced the drive belts recently and within a few startups, noticed an intermittent knocking sound coming from the camshaft/water pump area. The noise is like two pieces of wood knocking on each other and it comes and goes. When the engine is hot it seems to do it less often. I am adding a video for reference.

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[AWD-Tony]

Not sure if this is the cause but harmonic balancer is wobbling. Inspect the rubber in the middle. They crack and the halves separate. This can cause major problems WHEN it separates. I wouldn’t start it until you fix this.

 

[Spleen8urLSX]

I’ve seen failing auto tensioners make a similar noise as well. It’d be worth pulling the cover and seeing if you can make the pin in the auto tensioner and tensioner arm move by flexing the timing belt by hand.

 

[jb705]

Not sure if this is the cause but harmonic balancer is wobbling. Inspect the rubber in the middle. They crack and the halves separate. This can cause major problems WHEN it separates. I wouldn’t start it until you fix this.

I have been suspecting the dampener because of excessive movement so i am just going to replace it asap. Will report back if that was the issue.

 

[jb705]

I have been suspecting the dampener because of excessive movement so i am just going to replace it asap. Will report back if that was the issue.

The harmonic balancer was the culprit. Replaced it today and the issue has disappeared. Confirmed the OEM balancer had partially separated. Thanks for your suggestions!