same here, fairly common on these cars as I have walked by others and heard the same.

 

Thanks for the confirmation guys.

It is quite a scary rattle and only happens when warm but goes away when you apply throttle. Are you guys experiencing the same too?

I would imagine as long as the rattle doesn’t get louder with revs/throttle, then it’s ok right?

 

S2000 has slipper pistons,ie very short<less drag> like a race engine.Its all good

 

Thanks Noodels!

Can I confirm the rattle was on warm engines? I see cold piston slap threads and goes away when warm. But not many of piston slap while warm but goes away with revs

 

We are not talking about a rattle. This is a specific sharp tapping noise that comes and goes. 3-7 taps, then goes silent. Then returns. Then disappears. And so on…

This can happen cold, or hot. During hot idle, the spray from the oil jets is low. Just above idle, the oil spray under the pistons is mushroomed down when the piston is going down. The oil is forced into pinholes in the piston, directly flooding the piston skirts. It hydraulically stops the shifting of the piston, and the subsequent noise.

Oil exit holes, which originate underside of piston, directly about the skirt:



Oil entry holes, underside of piston:

 

Thank you for the explanation and reassurance Billman. Appreciate it and I can finally enjoy the car. Cheers!