The noise is normal and not harmful. It happens on both the Nissan Motorsports, Z1, GTM and Stillen kits from my understanding.
The reason we offer the center bolt is just in case you loose, trash or are not returned the factory center bolt when installing the Nissan Motorsports Oil Cooler Kit. Unlike the spin on type sandwich plates used in the Stillen and Z1 Oil cooler kits. The Nissan Motorsports requires that you completely remove the center oil filter bolt, replacing it with the longer OEM Nissan piece.
We have heard cases where dealerships and other like shops trash or fail to return the center oil filter bolt to the customer. This is BAD since the customer will not be able to remove the oil cooler kit and return the vehicle to stock without it.
It is also very likely that the center oil filter bolt is damged when initially removed, if not removed properly.
If you still have you original oil filter bolt and it is in good shape, then no worries. You do not need to purchase an additional piece.
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