95 Nissan Pathfinder cycling knocking sound.

Hi Guest,

When diagnosing odd engine noises, the purchase of an automotive stethoscope is key. Harbor freight sales one (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41966).

Other alternatives are available such as using a big screwdriver or pry bar. The screwdriver approach removes flexibility to check areas in difficult areas as well as forces you to lean over the engine which is a safety risk.

In either case, you stick the metal end of the stethoscope or pry bar against various components and stick your ear against the plastic end. Focus on pulley driven devices, the front engine cover bolts, the valve cover bolts, the ports of the exhaust manifold, and the block.

If the noise is around the drive belt area (or even close), remove all drive belts. Start engine (do not let run for more than 30 seconds). Does the noise go away? Add drive belts until the noise returns.

You pretty much have to narrow down where the noise is coming from to know which steps to take. From experience with Pathfinders, I would think AC compressor knocking or timing chain knocking.