PCV valve operation diagnostics on RB30 Patrol

[dom14]

Hi guys,
As you know, in RB30 Patrol, the PCV valve is bolted onto the inlet manifold, then connects to the rocker cover via a rubber hose.
I disconnected the PCV hose from rocker cover and blew into it. There's no air flow(it blocks the air flow).
I sucked on the hose. There is air flow that comes into my mouth and I can hear the PCV valve clicking.

But, I'm confused. Not blocking the air flow when sucking at the hose indicates the PCV valve NOT stopping any backfires getting into the crank case.

So can I interpret that as a faulty PCV valve??!!

Blowing at the PCV valve blocks the air flow from my mouth and I can't get any air into the inlet via the PCV valve that way.
So, how does the PCV valve allow the blow-by gas to get into the inlet manifold when it blocks like that when I blow into it??!!!

So, again, can I interpret that as a faulty PCV valve?!

Thanks for any help

[taslucas]

Is it ment to open the pipe up by "sucking" from the inlet manifold instead of "blowing" from the crankcase?

tappa lives!

[dom14]

Is it ment to open the pipe up by "sucking" from the inlet manifold instead of "blowing" from the crankcase?

tappa lives!

Yeah, that's my point as well. I don't think it's meant to do that. But, having said that, some PCV systems are not necessarily simple and the valve isn't that simple either.
Instead of a simple vacuum operated closing valve, it may be a spring operated control check valve.
Either way, the above behaviour still puzzles me.
I need some advice from a guru who understands the RB30 PCV system well.

Another thing that puzzles me is that there's another breather that comes out of the rocker cover(as in the picture) which connects to the air filter. That should do the job for fixing any excess blow-by as well as helping to regulate the blow-by gas back into the inlet, should it not?!!

I'm heading towards the direction of a dodgy PCV system in this RB30 engine.
I'm also wondering whether the PCV system in RB30 is all meant to regulate the blow-by gas into the inlet manifold or whether it has other more important functions in this engine?!

[dom14]

It sounds like that the "rattle test" or the "blow test" is by no means a conclusive or correct test to diagnose a faulty PCV valve.
Bit of internet reading on PCV systems and the spring operated PCV valves suggest that.

Any ideas guys??!!

[taslucas]

Is anything wrong with the operation of the engine? Could it be that everything is working how it's ment to be but the gasket is leaking?

tappa lives!

[nissannewby]

So you could have a blockage in the hose which connects to the pcv. The breather that goes to air should be plumbed into the air filter so it is under vacuum.

[dom14]

So you could have a blockage in the hose which connects to the pcv. The breather that goes to air should be plumbed into the air filter so it is under vacuum.

No blockage in the hose or the splash guards under the rocker cover or the hole on the rocker cover.
The venting of the breather that goes to the air filter is temporary thing until I put the air clean assembly back in.
The PCV hose is under vacuum, but I thought the second breather line being under vacuum may not be critical for my test phase?!

[dom14]

Is anything wrong with the operation of the engine? Could it be that everything is working how it's ment to be but the gasket is leaking?

tappa lives!

Yeah, I explored that possibility by installing a brand new gasket and a tightening it evenly and carefully the same way we do the head gasket bolts. I also used brand new rubber washers for the tightening bolts as well. It was still leaking from the back end of the gasket. Then I started fiddling with the PCV hose by pulling it out and allowing the rocker cover vent of the PCV hose to vent into the air. The blow-by stopped when I did that.

[mudnut]

Give Alitis007 a PM
and ask him.
He has a lot of
experience with
RB30's.

[taslucas]

He hasn't been on the forum for a while. I'll tell him to look. But all his experience is with efi rb30's so I'm not sure what differences there are

tappa lives!

[dom14]

Yeah, I haven't heard from George for a while on the forum. George advised me to go for EFI when I met him last time, but I still haven't got around to do it.
I'm not sure how the PCV system is set up in EFI RB30.
I'm ordering a PCV valve now. It's not that expensive and I reckon it's worth changing it anyway.
From my reading, passing the rattle test and blow test with flying clours is not necessarily a good indication of a good PCV valve.

[dom14]

I received the new PCV valve today. I'll fit it in over next couple of days and put things back together the way it was and see how it goes.
I'll update the outcome here soon.

[dom14]

Installed the new PCV valve today. I have to drive it for a while and see any improvement.
I think the old PCV valve is faulty. When I blew from each side, once side passed the air fine, the other side does it partially.
The new one, one side passes the air fine, the other side is hardly passing any air.
I will update how it goes with the new one.

[dom14]

I put the PCV valve to rocker cover connections back the way it was, then did few test drives with high revs.
There's no sign of oil leaks so far. So, I reckon the problem might have been rectified by the PCV valve replacement?