M35 Pcv Valve

[andy65b]

I am sure a few of you have read my posts about trying to get my idle right on my M35.

6 months of trouble shooting, a bit of money tossed away (fortunately not too much) and many hours of reading and thinking of a solution I worked out that it was a faulty PCV valve. Nissan could not work that out.

For those of you not familiar with this item it is a Positive Crankcase Ventilation Valve (PCV Valve), and it's role is to let air/gas that blows past the piston rings escape from the crankcase. If it can not escape it creates a lot of pressure in the motor which starts to create oil leaks at gaskets as the oil is put under a lot of air pressure especially in a turbo car.

There are pro's and con's about this gas being recirculated back into the manifold after the butterfly as it is putting oily, petroled air back into the cylinders which is not ideal for the performance of the car. This is why many high performance cars opt for a catch can but legally you are not allowed to vent this gas straight into the air.

Anyway it seems the more I have reserched it is a part that is normally serviced/replaced at a major service inerval.

The effects of a fauly PCV can be varied and will largely not be visible when driving your car but some of the signs can be;

- excess boost bleeding off

- idle not resetting correctly

- high idle

The PCV should under normal operation should operate the following way.

1) At idle: should not allow any gas into the manifold.

2) Under light to medium throttle: Suck open the valvewith the high vacume of the manifold and allow gas to pass to the manifold.

3) Under full acceleration: The pressure in the crankcase will push open the valve and allow gas to enter the manifold.

If you are trying to reset your "Idle Air Volume Learning" with a faulty PCV it will not set the idle correctly, as it makes the car idle faster and does not allow the car to memorise the idle (sets only between 600-700). If your idle is not in this range then you may well have a faulty PCV. (it is soooo niceeee haveing a car that idles at 625rpm )

The part number from Nissan is 11810-8J102.

Cost is about $50

Not generally held in stock and about 7 days fro Japan.

It is located on the top of the right bank (drivers side) near the front of the car. If you follow the metal intake piping from the throttle body to where it joins the rubber piping coming from the Intercooler, it is located just below this junction. It will have a pipe leading from the PCV back to the manifold (it is the one nearest the metal brace on the drives side of the manifold towards the cabin)(hope that made sense )

When I removed mine the valve was moving freely inside the the body, not only up and down but side to side. Whilst a new one will rattle when you shake it, it is not meant to move side to side.

I have spoken to a one other M35 driver who has changed his and he was shocked at how much less the boost bled off in higher revs.

I hope my 6 months of pain helps you guys avoid this pitfall.

Cheers

Andy

[[[d a n n y]]]

wooohoo

another usefull info for the m35 guys

im going to try this out 2nite

[scotty nm35]

Can any pcv valve be installed there? I just thought they all do the same thing dont they?

I definitely have to do this myself, same symptoms but not all the time.

[andy65b]

Can any pcv valve be installed there? I just thought they all do the same thing dont they?

I definitely have to do this myself, same symptoms but not all the time.

I am not really sure if you could put anything else in there. My gut feeling is no, as normally Nissan would have substitute parts listed if not available and they did not offer any substitute.

[lachlanw]

where did you get your info regarding to the operation od the pvc valve ? did you research it and the m35 works different to every other pcv valve ? and is it controlled electronically ? it could not function in the way you describe if not. and also a pcv valve and a catch can go in different parts of the engine ventalation systems

[lachlanw]

a pcv valve is merely a very lightly spring loaded one way valve . any valve that will fit the hoses is going to work fine

[andy65b]

I have just read the internet for general information.

You may be right that any valve will work but as I said, I am not really sure.

You are right in your description but I can tell you when it is not sitting right it can really stuff up your car.

I am not sure what you mean about the catch can but my understanding is that the catch can is used to filter oil out of the blow by gas before the air goes back into the manifold.

If you know better how the PCV works please enlighten us all.

Edited August 3, 2009 by andy65b

[zei20l]

the spring tension may be specific for a VQ25DET as we have positive manifold pressure, whereas every other VQ series motor doesnt (besides the VQ30DET)

so its entirey possible its different. however, FAST it and find out and post back in here!

and yes a catch can prevents the solid oil particles from re-entering the motor via the intake manifold. eventually the catch can would need to be emptied. but if your car can fill one within a few years, you have some problems.

the valve is also threaded at once end that screws into the rocker cover, so youd need one that fitted correctly there.

[iamhe77]

Good one Andy!

I am sure this will come in handy in time (I was reading this last night while looking over my mates M35)

As Danny said, just a bit more info for us M35 owners.