Found this in cfans....

'07 3.7 I5 Valve Cover..
Part Number is: 12603876

 

Awesome, thank you. This looks metallic (mine is the polymer one in 2005), but I bet it's similar. How the heck can those baffles move enough to let a lot of oil through? I could see how a little might escape, but I was not expecting it to look like that.

Thanks for the photos!

 

Same question. HOW does oil flow like a faucet through that. How does oil in engine defy gravity?

 

I'm guessing under that metallic shield, it's an orifice? There's no check valve or anything, right?

I'm still really confused as to why both sides (which are connected inside the head) are needed. Can I plug one side, put a T-connector on the other, and run one hose to the intake before the TB, and one hose to the intake manifold?

I've heard so many conflicting things about this system. I'm thoroughly confused. I recently heard (here) that the intake tube picks up air inside the intake manifold (like a Pitot tube) and air flows from the intake manifold to the valve cover, then air can vent from the valve cover to the TB.

It's confusing. And also getting a thin film of oil in my intake, so I want to solve it. I need a way of figuring out air flow direction in an air line. Seems like a good science project.

 

Ok, thanks. That helps. Why do I have oil in my breather then? What conditions would cause crankcase pressure to be higher than intake pressure?

I'm thinking (now) that I'll add a catch can on the intake side, and put a check valve on the exhaust side, that only allows airflow from intake to valve cover.

If it needs to relieve pressure from that line (I can't see why unless the other side was clogged, though), maybe I can put another check valve that vented positive pressure to the air (through another can that wouldn't get oil everywhere), just in case it needs airflow in both directions on the exhaust side.

 

If you are getting excessive oil usage check compression.

 

Here is a pic of the orifice. The one on the exhaust side is the restricted one that replaces a PCV vale.

The exhaust side

The intake side

 

Here is a pic of the orifice. The one on the exhaust side is the restricted one that replaces a PCV vale.

The exhaust side
(image removed)
The intake side
(image removed)

You say it's the exhaust side (connects resonator to valve cover exhaust side) that's restricted, but cart7881 says it's the intake side (connects valve cover intake side to intake manifold) that's restricted with an orifice.

3.5 Crankcase Ventilation System description, from the 2005 Service Manual:

A crankcase ventilation system is used to consume crankcase vapors created during the combustion process instead of venting them to the atmosphere.

Fresh air is supplied through a filter to the crankcase, the crankcase mixes the fresh air with the blow-by gases and then passed through a positive crankcase ventilation (PCV) orificed tube into the intake manifold.

The PCV orificed tube restricts the flow rate of the blow-by gases using a 2.5 mm (0.098 in) orifice located in the camshaft cover tube. If abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gases to back flow through the crankcase ventilation fresh air tube into the air cleaner resonator in order to be consumed by normal combustion.

At least I think we have the direction correct, judging from everyone's posts (thanks!). I'm assuming the orifice side will be the most likely to become clogged and cause problems, so I'm curious to know which side is restricted. I'm using about a quart every 7000 miles, and I think most of it is deposited on the back of the motor, just by looking at it. That's not bad for a motor with 170k miles on it, I think.

 

3.5 Crankcase Ventilation System description, from the 2005 Service Manual:

A crankcase ventilation system is used to consume crankcase vapors created during the combustion process instead of venting them to the atmosphere.

Fresh air is supplied through a filter to the crankcase, the crankcase mixes the fresh air with the blow-by gases and then passed through a positive crankcase ventilation (PCV) orificed tube into the intake manifold.

The PCV orificed tube restricts the flow rate of the blow-by gases using a 2.5 mm (0.098 in) orifice located in the camshaft cover tube. If abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gases to back flow through the crankcase ventilation fresh air tube into the air cleaner resonator in order to be consumed by normal combustion.

 

^ that is spot on. Thanks for sharing!

There's always a lot of confusion around breather/pcv systems. I feel like that post would make a good sticky on how the system actually works.

 

I went back out to my garage this morning and Cart7881 is correct the orifice is on the intake side. I was looking at the whole openings only but when I looked down into the opening I see the restriction. Sorry for the misinformation and confusion I may have caused. here is a pic of the orifice.

 

I went back out to my garage this morning and Cart7881 is correct the orifice is on the intake side. I was looking at the whole openings only but when I looked down into the opening I see the restriction. Sorry for the misinformation and confusion I may have caused. here is a pic of the orifice.

Hey no apologies, you've helped a lot! Thanks!

 

aww man ive always wanted one of those! for uhh... research purposes..

as far as the rockers and lifters, without removing the cam...no clue.

 

 

Thanks for this picture, too. Looks like the polymer is the same as the metal cover.

Crazy idea: You can't vent the passenger side port to air without throwing a code. My guess is that it allows air to be drawn into the crankcase, then flows into the intake to be burned, without going through the MAF sensor first (so it would be lean).

If I stopped up the driver's side port (both on the valve cover AND the intake), then vented the passenger side with one of those vented catch cans, would it work? If the crankcase pressurized, it would catch the oil in the can. If it built up vacuum, it would draw filtered air into the crankcase.

Second thought: Does the throttle body fully close? If so, it seems that at or near idle, nearly 100% of air would flow through the crankcase first. I wonder if I did that if I would have to put a small hole in the TB to allow air in the way it's allowed in through the crankcase now.

 

As far back as I can remember, engine were vented. Prior to the PCV Systems, the vent was nothing more than a cap attached to the valve cover. It was removable for cleaning. I'm sure that there is still a need to vent the engine, probably to prevent pressure buildup that could cause blowby. If you were to block the exhaust port that goes to the intake and attach something to the inlet side, it might create breathing problems.

The throttle body plate never closes fully. It is spring loaded to a partially open, default position, to provide airflow at idle.

 

I need some help to get my head wrapped around the purpose of a "catch can" on a stock, daily driver vehicle. I understand that vehicles with high compression/high horsepower engines, in race mode, would develop excess internal pressure, and would need a method of capturing the venting.

On a stock engine, such as we have in our trucks, the crankcase venting is accomplished by fresh air entering the engine through the resonator, circulating in the engine, and exhausting, as a vapor, into the intake, where it mixes with the intake air and passes through the engine. Most of the time, the intake will be warm/hot enough to maintain the vapor state.

Now the part that I don't understand. It appears that a "catch can" is a sort of filter that is attached to the crankcase vent exhaust port and either open to atmosphere or routed back to the intake manifold. The vapors are routed through this "catch Can" and the resulting liquid that accumulates inside is periodically emptied out.

Why would this be considered a viable alternative to a properly operating OEM crankcase vent system? I have seen pictures of "catch can" setups, where guys are showing filter bowls with liquid in them and claim that they have "saved" their engines from disaster. To my understanding, they are only routing the normal vapor, from the engine, to a cool area where it condenses into a liquid. That's what happens when you cool a vapor. If it had been allowed to follow the OEM path, it would have been consumed in the engine.

Someone please explain what I am missing here. It's a big subject over at C'Fans, where a lot of guys are chomping at the bit to install a catch can on their 2015 Colorados/Canyons.

 

I can only speak for myself (about to install catch can), all that it does (when installed with no modification) is improve the engine's ability to separate oil from crankcase gasses. I'm tired of fouling plugs. The system in many modern engines is not sufficient, and engineers have their hands tied to fix it.

The original design was to filter vent the crankcase to the atmosphere. Since there are hydrocarbons in the crankcase gasses, they are considered pollution. The solution is to vent those gasses into the intake to be burned. If they are vented into the crankcase to be burned, you need a source of filtered fresh air to replace it in the crankcase. If you were to put a filter to the atmosphere, it would make a path for air to enter the engine and find its way to the intake without being "seen" by the MAF, throwing off the A/F mixture, so it's drawn after the MAF.

From what I understand, nothing that is strictly emission controls can have scheduled maintenance in order to continue functioning, so this is why Chevy Performance makes catch cans for new cars (like the new Camaro), but is not allowed to install them at the dealership.

So, this is why the throttle body gets so dirty so often. This is why (I think) my plugs don't last that long. I usually have a think film of oil in the resonator when I take it off. The baffle system isn't effective at separating oil and air, and the catch can will improve this.

It doesn't help that the intake vent is orificed and can clog, and the tube makes two 90-degree bends, one of which is behind a heat shield that cannot be removed without breaking it (hence the dremel modification to the intake to get to the port).

If you don't see oil in your resonator, and don't hear lots of hissing gasses under the intake heat shield, there's no reason to modify your vehicle (unless you plan on off-roading a lot or doing something to splash a lot of oil around).

I'm ready to install a catch can, and even modify it to vent gasses to the air because I'm tired of dealing with the problems its giving me now that I'm over 150k miles.

Short answer: Catch can does what the valve cover baffles try to do, but do a better job. They can't be put on the car because GM can't put a pollution control device on the truck that requires maintenance (draining the can).

It also doesn't help that the oil that isn't supposed to be there softens the vent tubes and makes them leak easily.

 

Well, with millions of vehicles operating without these "catch cans", and a lot of them having several hundred thousand miles, it seems to be a relatively few people actually need one. It appears to be a bandaid fix to use instead of repairing the OEM vent system. I'm still not understanding, if this is such a great feature, why it isn't in widespread use, and why would one want to install this on a brand new engine?

Maybe I'm still missing the point. We aren't talking about a "mass" of oil flowing through the vent system. Of course if you condense the vapor, in a container (catch can), over a period of time, it will appear excessive, when in reality, it doesn't amount to much. If an excessive amount of oil was being lost through a properly operating vent system it would show up as a loss on the dipstick and there would be complaints.

On a high mileage engine, worn rings or valve seals probably contribute more to plug fouling than vent vapors.

I'm not sure why the vent vapors would be causing excess throttle body problems. The vapors go to the intake manifold, thereby bypassing the throttle body.

Okay I'm still in the learning mode. Do you have a link to the Chevy Performance catch can? Do you have pictures of the camshaft cover with the plates removed?

 

Oil fouled plugs mean internal engine problems. Usually if you have oil getting into the intake it's bad rings or pistons. Time for a leak down test.

 

You're right. A leakdown test is never a bad idea. I'd probably want to do it myself to see if I can hear air leaks if a have a high-leakage cylinder (because I wouldn't know if it was the rings or the valves).

My plugs now aren't that bad, and I'm not fouling them quickly, but they do show signs of burning a bit of oil, and I have oil that's leaking around the loose vent hoses on the valve cover (assorted hose clamp kit should be here today so I can fix that), and there's a thin film of oil in the resonator box.

Still, never a bad idea to do a leakdown test.