vaccum leak from pcv valve?

[chmercer]

my pcv valve on my KA is open air (the holes on the manifold are welded closed) and ive been trying to find boost and vac leaks. so i have the turbo inlet capped and a compressor hooked up doing 20 psi. and the pcv valve is just dumping air out. is this how the pcv valve is supposed to work? it seems wrong to me for it to just dump air out under boost.

does anyone have any info on this?

[S14DB]

Is your Valve cover intake hooked up to the charge pipes? If so you're pressurizing the Block and it's bleeding out the PCV. Will prolly kill the PCV and some of the seals in the engine if not the rings.. Best is to have the Valve cover hooked up to the turbo intake piping if MAF. If IAT+MAP Then to the atmosphere is fine. Prolly a good idea to hook the PCV up to a catch can and then to the intake so the vacuumed can scavenge the crankcase gasses.

You could also have a bad ring. But I hope it's not that.

[chmercer]

the one on the crank case goes to a catch can and the catch can pulls vaccum off the intake manifold.

im not really sure what your talking about, you say charge pipes and turbo intake pipes like they are different things?

[S14DB]

The Crank Case is the block. The case for the crank.

The Valve Cover on top of the motor there is a port that is the PCV system intake. In stock configuration it takes metered fresh air from the intake.

The PCV valve is on the crank case/block. In stock configuration it pulls crank case gasses from the block. Sealing during boost and backfire not to pressurize the crank case.

Charge pipes are the pipes in a turbo system that see boost. Hot pipe, cold pipe, IC pipes ect. Intake tube is what the Air filter, MAF, BOV recerc, vacuum ports hook upto.

Are you running a MAF or MAP+IAT? if MAF the Valve cover should be hooked upto the intake pipe behind the maf to meter the air and not stumble and have a hard time holding idle. If MAP+IAT you can have it open to the air with a filter. Having this hooked up to a boost sorce will pressurise you block blowing seals and heavy ring wear.

The PCV port on the block should be hooked upto a catch can and then to the intake to see a constant vacuum. Hooking it upto a boost source will reduce the scavenging and blow out the PCV valve since it's only used to seeing boost in back fire conditions.

I'll try to get a picture from the FSM to help in a bit.

[S14DB]

Air goes in, picks up the crankcase gasses and blow by then exits thru the PCV valve.
http://img.photobucket.com/albums/v108/S14DB/240sx/Engine/PCVdiag1.jpg
Only time it would come out of the Valve cover is if your rings were so shot that you outflowed the PCV valve.

[chmercer]

sorry it was early when i posted that, haha.

my valve cover outlet thing goes to a catch can which also has a line on it hooked to the intake manifold to pull vaccum. the pcv on the block is open air no filter.

so you say the pcv valve should be sealed under boost? when i pressurize the system it just dumps air out. so maybe it is jammed open? and i wasnt noticing it as much when i had it recirced into the intake manifold because it wouldnt be causing a megazord vaccum leak?

"The PCV port on the block should be hooked upto a catch can and then to the intake to see a constant vacuum. Hooking it upto a boost source will reduce the scavenging and blow out the PCV valve since it's only used to seeing boost in back fire conditions."

so i cant just leave it open? i was "trying" to not recirc the blow by into my intake.

also i dont get it when you say hook it up to an intake source, but not a boost source. the stock configuration puts it on the intake manifold which would be pressurized under boost, so, ?

thanks for helping :)

[chmercer]

oh yeah and the car is maf

[projectRDM]

The PCV system is mounted on the lower front timing cover. The breather sits off the side, just below the head, and the valve itself is threaded in behind and plumbed in below each intake runner. On an OE setup, vacuum in the manifold pulls vapors from the block and reburns it in the engine. I think we had talked about plugging those ports like I did, so what you're saying is the valve itself is blowing boost, correct? Replace it and see what happens. It should be just left open.
As for the valve cover, the port on it is just a vent for the head/block, pulling suction under vacuum. With a boosted car it needs to be plumbed into the intake pipe or sent to a catch can.

[chmercer]

here is a pic to hopefully make my setup a little more clear, im at school and dont have my car or else id take a picture

http://img180.imageshack.us/img180/3166/pcvsz9.jpg

from my understanding i need to move the vac line from the intake manifold to my turbo intake pipe for it to work correctly? because it will be pulling vaccum at idle which will be fine, but under boost it will pressurize the catch tank backwards from the intake manifold and pressurize the crank case which is why im getting hissing out of my pcv with the motor off.

[McRussellPants]

You should T the crankcase breather into the valve cover breather and then run the line to your catch tank and then to the intake before the turbo.


bada boom, SR style breather system that only sees vac.

[chmercer]

gonna run a line to the catch can from the pcv, does anyone know what size the pcv barb is, does 5/8" sound right? ordering crap off summit

[Buffalo Daughter]

yeah thats sounds about right if you add a t fitting back to route it into the or manifold somewhere or valve cover . The original design of it goes from the valve cover to the intake. And from the pcv to the manifold. So really you need to make a loop. I'd think your be losing a lot of pressure if you leave it exposed to air.

how about extending the pcv valve out more so you can get to more easily while your doing that and then figure out the routing. Just run a hose long enough outward. I would that would be a smart idea if your boosting and prolly the pcv is going to get gunked up with sludge and carbon. just my thoughts :D

[S14DB]

sorry it was early when i posted that, haha.

my valve cover outlet thing goes to a catch can which also has a line on it hooked to the intake manifold to pull vaccum. the pcv on the block is open air no filter.

so you say the pcv valve should be sealed under boost? when i pressurize the system it just dumps air out. so maybe it is jammed open? and i wasnt noticing it as much when i had it recirced into the intake manifold because it wouldnt be causing a megazord vaccum leak?

"The PCV port on the block should be hooked upto a catch can and then to the intake to see a constant vacuum. Hooking it upto a boost source will reduce the scavenging and blow out the PCV valve since it's only used to seeing boost in back fire conditions."

so i cant just leave it open? i was "trying" to not recirc the blow by into my intake.

also i dont get it when you say hook it up to an intake source, but not a boost source. the stock configuration puts it on the intake manifold which would be pressurized under boost, so, ?

thanks for helping :)
The PCV valve should seal when it sees boost. You have it venting to the atmosphere.

The KA system was designed to run NA not under boost. Changes need to be made.

You have a MAF so all lines have to connect behind the MAF. If you don't you'll have unmetered air entering or leaving the system. Causing a rich or lean condition.

You need to plumb both those lines between the MAF and the Turbo(Assuming you're not blow thru) in the intake. The line from the VC should be intake only. You shouldn't need a catch can. The PCV you should run to a catch can stuffed with SS wool to catch any oil. The gases shouldn't be that bad.

[chmercer]

http://img182.imageshack.us/img182/681/pcvsz9yf1.jpg

ok so im gonna be doing it like this

i am almost 100% that this way it should be fully functional as intended, and not barf any oil in my engine bay or on the ground.

instead of running 2 lines like you said ill just run them both to the catch tank for sake of simplicity and have a single vac source.