PCV Valve - How do you know

[floatingkiwi]

if it is knackered or not?
A little bit of help with the function of it would be helpful too.

Cheers

[huck369]

If your Oil dipstick keeps blowing up about an inch, the PCV is probably bad.

[floatingkiwi]

I don't have that issue (wipes forehead and touches wood) but seem to be sucking an awful lot of oil thru the vacume lines. Back to the drawing board.
Thanks again.

Matt

[svxistentialist]

Matt

I think the PCV valve is cheap, and should probably be renewed when the car has 160k kms or 10 years on it. I am doing mine shortly.

Don't know much about the vacuum lines you mention, but there is an emissions system that relies on vacuum, the EGR circuit, for Exhuast Gas Recirculation. It use that canister thingy behind the headlight. This circuit contains at least two valves and an EGR solenoid valve. My uneducated guess here is you have a faulty or stuck valve here somewhere.

Write up a description of what is happening and ask on the Technical Forum. Todd or Beav or some of the guys will respond for you.

Joe

[Beav]

The canister is for storing gas fumes from the gas tank. When the engine is started the fumes are evacuated and burned in the engine instead of being dumped into the atmosphere. Abnormalities in this system may or may not set codes on OBDI cars, definitely will set codes on OBDII cars - very sensitive.

The EGR system is a way of introducing an inert gas into the combustion chambers, keeping flame propagation under control and thereby reducing/eliminating detonation and keeping the level of NOx in check. Any deficiencies here will cause the Check Engine lamp to illuminate (fairly sensitive system.)

PCV systems were introduced in '63 and modified to their current design in '68. The design is old and totally inefficient for current fuel injected engines. This is a huuuuge problem for all cars today, oil is pooling in intake manifolds, running down and collecting and coking on injector tips causing poor spray patterns. The oil also makes its way into the combustion chambers, building enough carbon on piston tops to cause interfernce and resultant noise as it strikes the cylinder heads. Ask a Cadillac mechanic about Northstar engines and knocking noises. The carbon on the pistons also causes pre-ignition resulting in the knock sensors telling the ECM to retard the timing and reducing power and MPG.

This same oil is also backing up and clogging throttle bodies and idle air controllers, as many of you have experienced on the SVX. Like I said, this is a huge problem.

In the near future watch for electric heaters and evacuation pumps to begin showing up on cars. This is one of the reasons for cars going to 42 volt electrical systems.

In the aftermarket some of us are beginning to install water separators for air compressors (you can pick up cheap ones at K-Mart, etc. for under $20) in the PCV vacuum line on the more sensitive and problem-plagued cars (include that Z06 in this list.) These separators work by spinning the airflow and allowing centrifugal force to separate the oil from the air. The collection bowl is then drained at each oil change. It's cheap and it works.

So, to finally answer your question, if you are seeing oil inside the vacuum lines you're overdue for a PCV valve replacement and a good throttle body cleaning is probably in order also. This may also help reduce/eliminate engine oil leaks. Just don't plan on doing this next Saturday, it is the Kentucky Derby, you know.

[svxistentialist]

Thanks Beav.

Better stop talking about it and get mine done pronto, then.

Joe

[floatingkiwi]

Thanks Beav. Sounds like this little baby could be the problem. Just cleaned the throttle body recently and it was full of oil and hard deposits along with the idle controller. I suspect this could also be the reason for my lack of low down torque and Low MPG.
Just a couple of questions though:
What the heck is OBDI and II?
I guess the PCV is just a one way valve to let excess crankcase pressure back into the inlet manifold system, and not oil - which I guess (I said that again!!) could be my problemo?
Cheers

Matt

[floatingkiwi]

Beav, ignore the dumbass question about the OBDI. I did some research (just like I should have before I asked). Oh the humility..
Matt

[Beav]

Actually there never really was an OBDI spec, it's just a colloquial term for pre-OBDII vehicles.

The PCV valve is a calibrated vacuum leak that pulls blow-by (air that slips past the piston rings) from the crankcase. This air has oil vapors included, that explains the residue/build-up in the intake system. Prior to the PCV system simple 'draft tubes' were attached to the side of an engine's crankcase. A steel mesh supposedly separated the oil from the air - it didn't. A tube would then allow the oil to drip onto the pavement below the engine, not a very enviromentally friendly situation.

Savvy racers these days are affixing electric evacuation pumps to their crankcases. Pistons descend into a vacuum much easier than into atmospheric pressure.

[floatingkiwi]

I wonder how easy it would be to install one of those pumps....
oh, bugger, time to wake up...

Matt