PCV valve replacement for 90+ Nissan 300ZX

By Brian Duley

Reason for replacement

The PCV valves get clogged with oil over time. This leads to a buildup in crankcase pressure. I can cause you dipstick to pop out, covering everything on the drivers side of the engine with oil. More seriously, it can destroy you rear crankshaft oil seal. Then you will then have a big puddle of oil in you garage that seems to mysteriously leak from some where between the engine and the transmission. To replace the oil seal you have to remove the transmission. The PCV valves cost about $4 each and is a good idea for preventive maintenance. My rear crankshaft oil seal started to leak at 70K miles. I replaced the PCV valve and it reduce my oil puddle size by 80%. After upgrading by 90 TT to stage 3, I needed a new clutch. I replaced the clutch and the rear crankshaft oil seal at the same time. Now my car does not drip any oil.

Parts needed

The PCV valves are metal spring loaded valves. I replace mine for Courtesy Nissan for $4 each. You also need to buy the new hoses because the old ones are too stiff to put back on. Mine were so hard that I couldn't get the driver side one back on. You could probably clean the PCV valves, but the part cost is minimal compared to the labor. You can also buy them at most auto parts store. Nissan puts the same ones on most of the V6 engines. If you buy the PCV valves from a parts store, you need to buy some straight PCV hose (it is oil resistant). I would also recommend getting four stainless steel hose clamps that screw tighten to replace the Nissan factor tension clamps.

Tools needed

The PCV valves are in such a tight spot that about the only tool you can get on them to get them in/out is a 19mm deep socket with several extensions and u-joints and a ratchet. And you need a long handled pair of needle-nose pliers to get the hose clamps loose. Be prepared to take loose the fuel filter mount, cruise control mount, and basically everything else you can possibly move to get more room for yourself. The hardest part is getting the hoses off and putting them back on. With a little patience and the right tools, you can do it.

Location

Right by the dipstick. It screws into the bottom side if the intake manifold and a hose comes out the other side of the PCV valve. You probably want to replace the PCV hoses also because they are had and brittle. The second PCV valve is in the same location on the other side of the car. Do the passenger side first because it is much easier.

Nissan Service

Your Nissan dealer may charge anywhere form $70 to $200 to replace them. I have heard several Nissan mechanics talk about how this is one of their least favorite things to do on these cars because it is in such a tight spot.