Cylinder Head Looks Steamed Cleaned
 

I bought a motor to replace my current seized motor. Sadly I don't know much about the new motors history so when I removed the valve covers I noticed the passenger side cylinder head has a steamed cleaned look. From there I pulled the oil pan off and noticed some "chocolate milk" in the very bottom. About 1/4 cup of water was in the oil as well. So clearly I have a leak (heads and/or intake). Pulled the heads off but didn't notice any visible signs there that would explain a leak. The head gasket doesn't appear to have any cracks in it. The valve areas in the cylinder heads are not steamed cleaned just the topside where the valve springs and rocker arms are. This is a W series motor supposedly from a Maxima. The engine I am replacing is from an 1986 300ZX A/B motor. I was able to confirm this by finding the stamping on both blocks. I checked the block deck and the cylinder heads and they both look good and within tolerance (.004).

My question is what would cause the topside of the cylinder head to be steamed cleaned but nothing else? Only that I can think of is maybe an intake manifold leak? Should I inspect the crank and rod bearings for excessive scoring due to the coolant in the oil pan? Been using the googlizer a good bit haven't found anything concrete related to my issue.

Just trying to see if anyone else has had this experience and what my next steps should be.

It really doesn't matter where the water came from or why the rockers and cams were so clean. With the amount of water in the pan and the appearance of the oil, I wouldn't trust the bottom end of the engine to last very long. I would tear the engine down, or perhaps swap it for another engine if you bought it from a reputable salvage yard. If you decide to tear it down, find a good machine shop that can assess the condition of the crank, block and magniflux all the castings for cracks.

good chance
 

I would say there is a good chance in cleaning the motor up for sale that water got in the engine, certainly a possibility you wouldn't want to overlook.

Maybe yes, maybe no.
 

Yes, I agree that this is a possibility. I considered saying something to address the water washing, but why would you remove the cam covers to power wash underneath them? Regardless, I still think it would be prudent to inspect the main and connecting rod journals on the crank if the engine is to be installed. Why invest the time to swap out the motors if the replacement engine tanks after little use.

FYI, I had a '93 Maxima GXE with a W-series VG30E. In 2004, it went to college with my son. Needless to say routine maintenance went out the window. First time it overheated on him, one of the cylinders went dead. My mechanic at the time told me the head castings on these engines were prone to cracking between the exhaust and intake valve guides on the middle cylinders of each bank under such conditions. The cylinder lost all compression, but no coolant space was involved. The engine ran surprising well on 5 cylinders. The car never left town after that, but another child at home drove it another 3,000 miles back and forth to school before I sold it. I've since run into other 90's vintage Maxima, Pathfinder and pickup truck owners with a similar experience. Perhaps the top side of the heads were cleaned looking for a crack? Just speculation.