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'08 SRX V6
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542 Posts
Discussion Starter · #1 ·
If you've changed your air filter, and tugged around a bit on the large air inlet hose while getting the airbox lid off, YOU SHOULD CHECK THIS.
If you had the quick-lube kids change your air filter, you DEFINITELY better check this.

There is a small hose, about 1/2" diameter, that exits the big air inlet hose between the air filter box and the throttle body. It is the Positive Crankcase Ventilation (PCV) hose. It quickly disappears under the engine shroud and heads rearward. It attaches to a grommet in the rear of the driver-side valve cover.
It doesn't have a lot of slack, and the grommet doesn't hold it too tightly, AND IF YOU MOVE THE BIG AIR INLET HOSE VERY MUCH THE SMALL PCV HOSE CAN BE PULLED OFF THE GROMMET BACK ON THE VALVE COVER.

Luckily, it's easy to see if you know where to look. Just look under the rear of the engine cover, right on the top of the valve cover. You will see the PCV hose attached to an elbow grommet which is inserted into the valve cover.

If this little hose comes off, the engine PCV system will be sucking unfiltered air into the valve cover/crankcase. Also, the throttle body will be sucking some unfiltered and unmetered air into the intake manifold. So, you end up getting some dirt into both the oil and the cylinders, and maybe a lean computer code.

WORTH CHECKING, AT LEAST EVERY TIME THE AIR BOX IS TOUCHED.

DG
 

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2004 SRX V6 RW
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76 Posts
Here's what I did to eliminate the potentional problem and also to never have to clean out the oil that tends to collect and accumulate in the air intake tube. Throttle body also seems to stay cleaner. From Home Depot I got an air filter for a lawnmower engine it is siliconed on to the elbow and a short bolt is used to plug the air intake tube. 04 with 74,000 miles.....
 

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11 CTS-V Sedan, 07 Corvette Convertible
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237 Posts
The PCV is a one way valve that only allows crankcase vapors out, not in. With the PCV system is connected to the intake because the air rushing through the intake creates a slight vacuum, which pulls vapors out of the crankcase. Your mod eliminates the vacuum and the oil and vapors that escape will quickly clog the inside of the filter. The PCV system is connected to the intake, because these crankcase vapors are the leading cause of hydrocarbon emissions from internal combustion engines. By routing the crankcase ventilation through the intake, they get burned in the combustion process. Once the filter gets clogged (and it will very quickly without frequent replacement) I have no idea what it will do to your engine, but I know it can't be good. You also significantly increase the risk of fire because the escaping hydrocarbons will collect in the engine compartment and are flamable and potentially explosive.

If you want to eliminate most of the oil that goes into the intake, you should look at adding an "oil catch can" between the PCV valve and intake.
 

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2004 SRX V6 RW
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76 Posts
First of all, the PCV valve on the 3.6 V6 is nothing more than a 3mm sized holed restriction, it is NOT a one way valve. It still functions like it was designed to with this mod.
The 3mm sized hole allows limited engine vacuum to pull air and vapors through the engine block originating from the passenger side and pulling it through the small air filter on the drivers side to be dumped into the intake manifold. There is no "fire" danger, older engines have used this design for many years without problems. It has worked for a long time for me, check out the factory shop manual schematic and operation description and you will see how this works.....
 

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'08 SRX V6
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542 Posts
Discussion Starter · #5 ·
Well, I agree somewhat with both of you guys. This is not the reason I started the thread, but I have plenty of experience with modified PCV systems in Corvettes.
Yes it's a fixed orifice metering hole, about 1.2mm if I remember correctly. Running at part throttle with some engine vacuum , the system neither knows nor cares whether it gets it's clean air from the intake bellows or a separate filter; either way it's routed through the crankcase and sucked into the intake manifold (where it deposits a bit of oily residue).
However, when the engine goes full throttle, the system reverses; there is no vacuum in the intake manifold and there is blowby pressure in the crankcase. This forces oily air backwards out the PCV intake tube. Normally, this blowby air is routed (and sucked) into the intake bellows via the little tube, and the engine again consumes the mess (again leaving more oily residue on the throttle body and intake floor.
Some of the Corvette guys use a valve cover filter as described above to reduce the full-throttle blowby gasses and oil into the throttle body and engine, when the car is tracked a lot and sees a lot of full throttle. Yes, the filter gets dirty when using full throttle a lot (but it doesn't get into the engine's intake and cylinders), yes the blowby vapors are released under the hood, not under the car like the old draft vent tubes; and yes it pollutes more than the EPA will allow.
So, yeah, on a lightly driven luxury wagon, the added filter will likely stay clean a long time, but subsequently will not serve much purpose in keeping the intake/throttle body cleaner. If you drive it hard enough to be effective, check it periodically, it will gum up with blowby residue.

DG
 
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