hacim105

iTrader: (6)

Can someone explain to me the purpose of the PCV valve. What is the reason for that whole system? I read through the FSM, that explains what it does and how it operates, but it doesn't explain why it's needed.

lowrider4lyfe

The PCV valve is just for emissions I think? It lets air get circulated through the engine.

whiteSE

iTrader: (2)

what it does, is keeps the pressure same everywhere (heads, block, oil pan)

njmaxseltd

iTrader: (19)

PCV = Positive Crankcase Ventalation

Keeps the crankcase pressure at a neutral state by allowing it to breath into the intake path.

tbergma1

I plugged mine up. Because you already have a crankcase breather hose connected to the front valve cover. Also if you look towards the left side of the motor (looking at it from the front) you will see another tube that jumps from the back VC to the front VC. I disconnected the front tube from the air box and put an air filter on it. This way that shiat doesnt go in the intake. That shiat will buildup on the valves and the top of your piston, its called carbon. WHen i need to smog it i put everything back the way it was.

nismology

iTrader: (8)

Poor car. You better be changing the oil every thousand miles otherwise contaminated oil is flowing through your motor.

tbergma1

How is it getting contaminated?, the oil never left the engine and there is no opening to let contamination in. I have an air filter on the end. You do not make sense.

nismology

iTrader: (8)

Do you know what the purpose of the PCV system is?

tbergma1

Yah, when there is positive pressure in the crank case (WOT) it vents through the PCV valve. But when you already have a breather hose on the VC's you dont need it.

You still havent explained to me how my oil is getting contaminated by not having a pcv valve, and having to change it every thousand. I would like to hear your opinion. Maybe i am missing something here.

nismology

iTrader: (8)

Guess not. A couple thoughts:


1. The PCV system is not active at wot since there's no vacuum.

2. The purpose of the breather tube that goes into the intake is to allow filtered and metered air to mix with the blow-by gasses in the crankcase and go to the intake manifold. The crankcase breather on its own is useless without a vacuum source to get it all moving, though. When the system is working properly, air is being sucked INTO the breather tube on the front valve cover and out of the PCV valve, not being pushed out.


Ergo, all that blowby gas and moisture is trapped in the crankcase with no positive way to vent it the way you have it set up now. That stuff ends up in the oil and contaminates it in short order. That's what the PCV system helps avoid.

tbergma1

That totally makes sense. Not to mention, the gasses that build up in the crankcase are somewhat explosive. I used to drag race and we removed the PCV system and went with an oil breather box instead. I hated all the oil buildup in the intake, valves and pistons. I guess the oil breather box shouldnt be used on daily drivers. I had my tube dip low at the end so that the oil would drip out.

Now i have an DIY oil catch can, seems to work, it already has some oil at the bottom.

nismology

iTrader: (8)

Is the PCV valve operational now? That's really the most important part of the system.

hacim105

iTrader: (6)

I'm so glad guys like nismology still exist on the org. They are so incredibly helpful. Thanks for your knowledge.

MOHFpro90

iTrader: (11)

I understand what you're saying, but I have a question. I read somewhere (I think it may have been you that said it) that if you have a breather on the front valve cover, that you virtually have a vacuum leak. I understand the concept(because of the un-metered air going into the UIM), but my car showed no signs of a vacuum leak(high idle, varying idle, etc), in fact it idled lower than normal. Keep in mind, I have an 00VI, a33 IACV etc, so I couldn't tell what was to blame for the low idle. Just curious as to your thoughts on this.

tbergma1

I have a 91 mustang 5.0 and my vacuum is not that low because of the cam i installed. My car runs a liitle low and ruff, i believe its the vacuum not being low enough and the cam being aggressive. On my 97 max, when i plugged my pcv up on the intake it did not make a difference on idle or anything. On my 2000 max i have the DIY oil catch can.