two PCV valves?

I have replaced the PCV on the passenger side of the motor before, but what is the other one opposite of it on the driver side of the motor? Is that a second PCV? It connects to a plastic hose that connects to a rubber hose that attaches to the air intake.

I am trying to go over my hoses to look for vacuum leaks and just wondered what this thing is for. Is it bad if it is disconnected? When I installed my ZR intake, I noticed that it wasn't connected to anything. It was just sitting there. It doesn't seem to make a difference if it is connected to the air intake or not. It is not sucking or blowing any air out of it. Is it supposed to?

well as far as i know it is just a crankcase breather. im not sure but yes it is not good to have it disconnected. it will spew oil all over your engine compartment

That's the crankcase breather. It takes in fresh air and it's for positive pressure in the motor because the pcv on the other side discharges it back into the intake. It's not a valve or anything, just a tube in your valve cover.

I just unplugged it from the intake and started my car and nothing comes out of it. Nothing. If oil came out of it, wouldn't it shoot oil into the intake??

35th T-bird SC said:

That's the crankcase breather. It takes in fresh air and it's for positive pressure in the motor because the pcv on the other side discharges it back into the intake. It's not a valve or anything, just a tube in your valve cover.

Click to expand...

Does it ever have to be replaced? It doesn't seem to make any difference if it is connected or not. It was disconnected under my hood for god only knows how long...months maybe...

That's why it's hooked to the intake, because the pressure from the rushing air being drawn into the engine is higher than the pressure coming out of the engine so the fresh air goes in and not the oily vapor coming out. Some cars have a crankcase breather on there with a filter.

There's really nothing to replace unless you break it. Leave it hooked up though because a crankcase breather wouldn't be feasable due to the IC pipe being in the way.

Think of your engine as a closed container with 2 vents. One vent has a checkvalve that only lets air out, and has suction on it. The air comes into the other vent.

In in this "container" air, oil mist, and combustion gases form and are drawn out through the checkvalve.

Now since this air enters the engine it must be measured, or the AF will be off, because now you have air entering the tube after the maf and before the TB, this will be a very small amount at light throttle. Then you have air that enters the engine that bypasses the TB and making it harder to control idle since at idle vacuum is high and suction is more than it would be at WOT. This also adds unmetered air into the engine.

Jeff

You should hook it back up to the intake for a couple of reasons.
1. At idle the vacuum gauge will be farther away from 20.
2. The intake tube after the MAF is the source of air for the PCV system.
3. The system is meant to be closed so the MAF meters all air.
4. Unmetered air causes idle problems and maybe detonation depending on the location of the leak.

We had a Volvo in that smelled like blow-by inside the car, it turned out to be the same tube not being connected.
Good luck

yes it is just a crank case breather. if you leave it unplugged it will suck dirt into the crankcase.also if you have piston ring blow it will blow oil all over the engine compartment.it is hooked to the air cleaner not for the rush of air but because the air is cleaned. besides there is slight vacuum in the air cleaner assembly no positive pressure

Before the 60s they just used a tube to vent out the bottom of the engine bay or a cap on the valve cover. Then it was vented into the air cleaner, which made them real oily. Now, ours are vented just before the T-Body so any back pressure will be taken into the intake and reburnt, thats why we see dirty oil in front of our TB. The computer knows about this air b/c it has been measured be the MAF. Logic dictates a slight lean condition if you plug the hole on the intake tube and let vent into the air, since the computer is adjusting fuel for less air than there really is. Good luck

I stand corrected Phucker!

sorry if i sounded ticked off but i was bein nagged at while posting

Something that I think people neglect to realize is that Most All of the oil and crap gets into then engine from the engine running normally not from getting into boost all the time. It's just from regular old driving, Probably more than 90% of the grunge that gets into the system through the PCV valve and not the vent. I could go into all the dynamics of it but if you just sit ack and think about it you will understand.

Jeff

if we are speaking about the driver side vent tube....does anyone have the hard plastic line that goes under the SC that they would like to sell. I broke mine and had to peice it together with rubber line. I was considering a breather, but i'd rather just fix what i broke. I'm sure the rubber section of line is fine, but i'd rather have the peice of mind knowing that its replaced.

Road Draft Tube

For what it's worth and maybe even close to correct..

The tube mentioned earlier, that was used on cars from the 60's (and before), was called a Road Draft Tube that was generally connected to one valve cover, and in fact was slash cut and placed into the air stream under the car to create vacuum for crankcase ventiliation. There was usually a filter media equipped, removable cap on the other valve cover that allowed air into the system and also served as a place to add motor oil. One problem with this approach is that it really only worked when moving at a half decent speed. Pretty much worthless at idle, especially if you already had significant blow-by.

Ive made exhaust systems for bikes using the same principal, whenever we'd eliminate the airbox system by installing individual carb filters. We'd cut a 1/4" pipe nipple at an angle, weld it into the collector so the exhaust would provide a vacuum source, and connect it to the vent connection that had gone to the crankcase from the airbox.

The PVC system is a much better system and should be properly maintained and connected for general use. Positive Crankcase Ventilation is a lot better than the old way.

Just thought I'd add my two cents.

This sounds like a newbie question, but where abouts is the PVC on the passenger side of the motor? I'm formiliar with the location of the other, but didn't realize this car had two of them.

Also, when my engine was rebuilt my builder removed the tube and such from my drivers side crank and mounted a small purfilter breather (nothing fancy, yet functunable) however after reading this I think I will take the advice and reinstall the orginal hardware, for my car runs rich and also the smell of oil in the cabin has started to appear as mentioned.

Thanks for the thread.

-Tim

There's only 1 PCV valve, and it's on the pass valve cover, under the t-body linkage. It takes vapor from the engine and puts it into the back of the SC and some to the vacuum dist. The other end of the system gets air from the bottom of the intake tube and puts it into the engine on the front of the drivers valve cover. Vapor often flows the other way, from the drivers valve cover to the intake tube. Good luck