Smoke out the breathers......


New Member
May 25, 2001
After running the car a little while, and it is idleing, it will smoke a little bit out of the breathers on the vavle covers, or steam maybe?

What does this mean?

I have notched out the rubber groments half way to try and relieve some of the crankcase pressure also.

NO pcv, just a breather there also.
Probably a little blow by.
PCV is a good thing to have, because it evacuates the the blow by, and keeps the oil cleaner.

U might want to put back the pcv.
The pcv helps release some of the postive crankcase pressure also recycle air into the engine oil to keep it cleaner.
If u use the filter make sure it does not clooge up or u will get blow bye and a blown rear main seal.
you might want to try ATR's inline check valve-- works like a pcv but doesnt allow any psi past it.

my limited does this everytime i take it to bristol or bowling green. it just smokes a little.

when you say it has a filter in place of the pcv,.. im guessing your talking about the old pipe that went to the turbo on the pass side valve cover?
try the atr check valve 19 bucks no more leaks from my seepy rear main on the WE4
I'll second the check valve. I have the Pete Tomka one(prob the same as the ATR one) and it works well.
There's a reason for the PCV. You're finding out why, when they aren't working properly you end up with more problems.

Get a properly working PCV in there. And with the right PCV you won't need to worry about a check valve either.
turbo dave-
the atr pcv valve is a one way check valve, and works as a pcv valve too..
ive bought PLENTY if GM pcv valves from GM and NOT one lasted over 6 months with high boost.
the atr one is 19 bucks and i havent had any problems with them in years...
every car i work on in town gets the atr check valve before we start moddifying the car, just to make sure the crank case doesnt get pressurized.

i really dont understand the BIG deal with all the pvc posts...IF you dont have a sealed crankcase..i.e the factory set up...your pvc is doing verry little...yes the factory pvc worked under vaccuum...the pass v-cover vent at the turbo pulled the blowby ...sooo if you know use k&N breathers...explain HOW the pvc is effective??????...the pvc is welded up on my gn..i use an asperator on the downpipe to pull vaccuume on the pass side v-cover ....i've never had hi BLM's or ANY ill effects from removing thePVC....tricky that steam is blowby still have a sealing problem ! flame suite on later joe:rolleyes:
A little "smoke" (it's actual vapor) out of the breathers is perfectly normal...Inside when running things are hot and will have a tedency to give off some fumes. Now ALOT is a different story.
no flames here joe-
when you delete the vent tube leading to the turboon the pass side, you have lost your pcv system.
i was just pointing out that IF you use the stock pcv valve, that it will not seal under high boost. that is why i suggested in using the check valve instead of pressurizing the crank case more.
Originally posted by Quick6'n'-K.C.
no flames here joe-
when you delete the vent tube leading to the turboon the pass side, you have lost your pcv system.
i was just pointing out that IF you use the stock pcv valve, that it will not seal under high boost. that is why i suggested in using the check valve instead of pressurizing the crank case more.

Maybe everyone has forgotten that the PCV valve is under vacuum during normal driving conditions. It's purpose is to pull the vapors out of the crankcase (the smoke you see). It matters not whether it's pulling it from the vent tube attached to the turbo inlet or through the K&N breathers used to replace the tube. It still pulls a vacauum, and this pulls air into the vent/K&N and evacuates the crankase that way.
Replacing the vent tube with a K&N DOES NOT cause loss of PCV functionality. It's just pulling through the little air cleaner instead of a tube.

Oh, and BTW the ATR check valve Is certainly NOT a replacement for the PCV. It does not (unless they've recently re-designed it) have the proper metering calibration in the vacuum direction. Just adding my experiences with the ATR check valve. IF one wants to use it, OK, but I would recomend using in series with the right PCV, so that proper vacuum metering can still take place. In other words it allows TOO MUCH air to be pulled through when there's a vacuum present. This is unmeterd air and may cause problems. The PCV valve metering is calculated for in the MAF calibrations. The system knows aproximately how much air is getting around the MAF from the PCV, and this is accounted for. Introduce TOO much air through this check valve and the amount of air entering the engine by the "known" source is too much.

As long as you keep the proper PCV valve in place it will work just fine without the need for a check valve. No, PCV's don't last forever, it's just a matter of normal maintenace that I replace mine about 1 a year or less. That $2.00 you have to spend on one must be a terrible financial drain to resort to having to do without one.

And NO a little smoke out the breathers IS NOT NORMAL, under any circumstances. Unless of course your PCV is not working or missing.
Dave, When you say that the PCV is accounted for in the MAF calculations are you talking about something that is installed in an aftermarket chip burners program? You stated that the PCV brings in unmetered air. This is true if K&N breathers are used but in the stock configuration the PCV sucks "metered " air from the turbo inlet bell. Thanks !
atr's one way check valve does work, it replaces the stock valve..

it works like a pcv valve ( allowing vacuum to pull through it) and when you go into boost, it absolutley will not allow any psi to go past it.
kirbans does NOT ALLOW THIS TO HAPPEN. just in my experiance with these parts side by side in my hands.

i am under the impression that:

taking away the vent tube leading to the turbo DOES eliminate positive crankcase ventalation!! just cause you have a filter on your valve covers allows it to vent,,..... but there nothing to pull the positive crankcase pressure out of the motor under a load!!!!!!!!!!!!
just cause there is a filter there, that will allow it to breath, but not get sucked out like it was when you floor it and the turbo inlet bell sucks on the valve cover and PULLS the crankcase pressure OUT into the turbo inlet bell.
EXAMPLE - alot of fast non turbo cars take the valve cover breathers and run them into the headers to help pull the positive crank case pressure ( from what gets passed by the rings) out into the exhaust?

i am not wanting to fight about this, i just am stating from what i think works with our motors.
atr ONE WAY check valve, wont allow your rear main seal to push out. :)
do you agree or disagree dave?
ya know now that I think about it,,,mine was "fuming" UNTIL I installed a new PCV valve and then in quit.

Basically I was going on my observations of our Blower motor in the race car. Doesn't really apply to a street motor.
Dave is correct. You should only use the ATR check valve in-line WITH a proper AC Delco PCV valve.

The ATR valve alone is not the best way to do it as it is NOT calibrated correctly like the Delco PCV is.

The PCV valve does affect the MAF calibrations as the PCV is pretty much just a calibrated vacuum leak anyways.

Open breathers or not, you should still use a proper PCV valve to get rid of the excess crankcase vapors.

Race cars often use the breathers vented to the headers or exhaust to remove the quick buildup of crankcase pressures in the motor. This shouldn't be necessary on all but the most wicked street cars.
Following what Dave and Mark have said, the pvc sucks because it is under vaccum and it matters not that the valve covers have breathers on them. The fumes it removes are corrosive. Race engines probably don't benefit from the pvc as the oil is changed frequently and the engines may be opened up frequently. Street driven cars greatly benefit from the presence. Street cars with conventional chips should use a calibrated pvc for best idle-no harm in using the check valve in line with the factory pvc to prevent boost from pressurizing the crank case past leaky rings.
PCV is Positive Crankcase Ventilation meaning it IS going to scavenge the crankcase.

The PCV valve does NOT suck from the turbo inlet bell, it sucks from ABOVE the valleypan. The turbo inlet is the breather, or the atmospheric pressure point of the system. I dont buy the "PCV leaks under boost" crap. Its a load of crap. It doesnt leak more than your rings does it?

There IS a methodical flow to the PCV system. Breathers are there so the crankcase isnt sucked into a vacuum. Kinda like sucking on a straw in a cup with no vent hole. No the block wont collapse, but once thres nothing more to suck, it becomes innefective. The breather is the vent, the atmospheric pressure pushing down into the crankcase to the PCV's vacuum which is sucking vapors out.

A car without a PCV or other form of POSITIVE scavenging will be suseptible to moisture and acid buildup in the crankcase. As accidental proof, I did a head gasket on a Cougar 3.8 a few years back and forgot to push the PCV back into the valve cover. I started it up and ran it for oh, 10 minutes and there was milkshake on the bottom of the oil cap. Thought I screwed up the head gasket. But once I noticed the PCV and put it into the valve cover, the milshake soon disappeared. Additionally, from a performance standpoint, positive crankcase scavenging creates a negative pressure under the piston making it easier to be pushed down. Thats why the big boyz run some sort of PCV, be it a belt driven pump, or a venturi setup in a header primary/collector.

The PCV valve IS a metered air leak and IS accounted for in MAF or VE calcs in the ECM. Youd be SURPRIZED how many driveability problems are caused by a PepBoys "generic" PCV valve. Additionally for you emissions testing concious, tampering with the PCV is a EPA violation, so those of you "smogging" your cars, better ditch that checkvalve on the way to inspection :)

If you dont believe Dave and I, thats OK, keep on believing what u choose. Theres no gun to your head.

As for smoke out of the breathers, smell it, if it smells like exhaust you most likely blew a fire ring into the valley.
Excellent info here guys...who ever thought a $2.00 psrt would be so important (I'VE always run one in every street engine)
Hey Zam70,

How is my old car? It looks like your getting all the bugs out and really catching on. How your friends Dragcar?

Your right on this guys like Zam70 said who would ever know a $2.00 part would be so important:D
I am new to the GN scene.

I had changed my pcv a couple a months ago. I think i bought a purolator brand pcv valve from pep boys. I took the vaccum block off by the throttle body and noticed a little dark oil by the inlet passeges. Is this caused by a fualty pcv valve? I am going to change over to an ac delco brand soon. I have had a rough idle problem for some time now.