5.7 vortex Fresh air hose?

[Serolim]

On my 96, from a previous thread I talked about an oil mist getting into my intake from the fresh air hose, how exactly does this hose work?

Would having a filtered breather do the same thing?
Aside from it being burned.

Or is a vacuume being pulled on it?

Question being because I routed a baffled oil catch can into that tube, and the hose is MUCH longer, about 3 and a half feet. From where it's leading to the can, then back to the intake.

After about a 200 mile drive, mixed hwy/city I checked the can nothing in it. Dry as a bone. So 1, due to the hose being longer the oil part is not making it all the way up, or 2, it's not getting blown into the intake due to the length? Should I be concerned?

 

[carviewsonic]

The catch can I installed on my Impala makes a hissing sound when the engine is running, so I know that the crankcase air is definitely moving through it. The length of hose used shouldn't matter, as long as there are no leaks vacuum will pull air through the hose.

 

[The_Nuke]

Originally Posted by Serolim
On my 96, from a previous thread I talked about an oil mist getting into my intake from the fresh air hose, how exactly does this hose work?

Just so everyone is on the same page, Let me lay out my understanding of the systems being discussed -

The typical CCV system on most n/a engines will have 2 hoses on the outside:
1) The PCV line which delivers blow-by gases to the intake manifold to get burned with the incoming air/fuel mixture. The PCV valve will usually be on the valve cover of one of the cylinder heads, and it will flow gases out of the engine and into the intake manifold almost 100% of the time (the only time it does not is when the engine is at WOT and producing maximum torque, at which point the PCV valve will slam shut and the flow of gases stops).
2) The fresh air line, aka makeup line, that delivers fresh (filtered) air to the engine's crankcase to replace the blow-by escaping out the PCV valve. Also, t+he normal point of attachment is the air filter air box for the source air, and it will attache to the engine at one of the valve covers to route the air into the crankcase. The air flow almost always goes from the air box to the engine, but when the engine is at WOT and producing maximum torque, the fresh air line can actually reverse flow and deliver blow-by into the air box (and coat the backside of the air filter element).

Now, you said you are getting an oily mist in your intake from the fresh air line, but that seems counter to what I would expect. The PCV line is the hose that runs into the intake, and the fresh air line never touches the intake, only the air box and a valve cover. Did you mean the PCV line when you asked your question?

Originally Posted by Serolim
Would having a filtered breather do the same thing?
Aside from it being burned.

The same as what, coating the inside of the intake with oil? No, it would not,since it would be venting the oily mist into the atmosphere. But doing that is bad for the environment, not to mention it could result in drivablity problems if driven as street-vehicle.

Originally Posted by Serolim
Or is a vacuume being pulled on it?

- The PCV line allows the intake's vacuum to help excavate the blow-by gasses from the crankcase, via the PCV valve.
- The fresh air line (aka Makeup line) allows the vacuum in the air intake box to feed it a steady source of fresh air into the crankcase to replace that gas which is exiting the PCV valve.

Originally Posted by Serolim
Question being because I routed a baffled oil catch can into that tube, and the hose is MUCH longer, about 3 and a half feet. From where it's leading to the can, then back to the intake.

As long as the hose is not being crimped or crushed when you close the hood, it should be fine.

Originally Posted by Serolim
After about a 200 mile drive, mixed hwy/city I checked the can nothing in it. Dry as a bone. So 1, due to the hose being longer the oil part is not making it all the way up, or 2, it's not getting blown into the intake due to the length? Should I be concerned?


Verify the hose is not becoming impassable when the engine is running. Maybe the closed hood puts a crimp in it, or maybe the vacuum inside the hose is too much for the hose to withstand, and it is squeezing flat as a result.

 

[Serolim]

Originally Posted by The_Nuke
Originally Posted by Serolim
On my 96, from a previous thread I talked about an oil mist getting into my intake from the fresh air hose, how exactly does this hose work?

Just so everyone is on the same page, Let me lay out my understanding of the systems being discussed -

The typical CCV system on most n/a engines will have 2 hoses on the outside:
1) The PCV line which delivers blow-by gases to the intake manifold to get burned with the incoming air/fuel mixture. The PCV valve will usually be on the valve cover of one of the cylinder heads, and it will flow gases out of the engine and into the intake manifold almost 100% of the time (the only time it does not is when the engine is at WOT and producing maximum torque, at which point the PCV valve will slam shut and the flow of gases stops).
2) The fresh air line, aka makeup line, that delivers fresh (filtered) air to the engine's crankcase to replace the blow-by escaping out the PCV valve. Also, t+he normal point of attachment is the air filter air box for the source air, and it will attache to the engine at one of the valve covers to route the air into the crankcase. The air flow almost always goes from the air box to the engine, but when the engine is at WOT and producing maximum torque, the fresh air line can actually reverse flow and deliver blow-by into the air box (and coat the backside of the air filter element).

Now, you said you are getting an oily mist in your intake from the fresh air line, but that seems counter to what I would expect. The PCV line is the hose that runs into the intake, and the fresh air line never touches the intake, only the air box and a valve cover. Did you mean the PCV line when you asked your question?

Originally Posted by Serolim
Would having a filtered breather do the same thing?
Aside from it being burned.

The same as what, coating the inside of the intake with oil? No, it would not,since it would be venting the oily mist into the atmosphere. But doing that is bad for the environment, not to mention it could result in drivablity problems if driven as street-vehicle.

Originally Posted by Serolim
Or is a vacuume being pulled on it?

- The PCV line allows the intake's vacuum to help excavate the blow-by gasses from the crankcase, via the PCV valve.
- The fresh air line (aka Makeup line) allows the vacuum in the air intake box to feed it a steady source of fresh air into the crankcase to replace that gas which is exiting the PCV valve.

Originally Posted by Serolim
Question being because I routed a baffled oil catch can into that tube, and the hose is MUCH longer, about 3 and a half feet. From where it's leading to the can, then back to the intake.

As long as the hose is not being crimped or crushed when you close the hood, it should be fine.

Originally Posted by Serolim
After about a 200 mile drive, mixed hwy/city I checked the can nothing in it. Dry as a bone. So 1, due to the hose being longer the oil part is not making it all the way up, or 2, it's not getting blown into the intake due to the length? Should I be concerned?


Verify the hose is not becoming impassable when the engine is running. Maybe the closed hood puts a crimp in it, or maybe the vacuum inside the hose is too much for the hose to withstand, and it is squeezing flat as a result.


Very informative, but yes here lies my confusion. On the fresh air line I am getting an oil mist in it, and which coats my intake and throttle body.

So my understanding is on high throttle instead of sucking air in it's blowing vapor/oil mist?

So if I unplug it from the valve cover, at idle I'd feel a vacuume, and at high throttle a pressure?

I can't figure out how to post pics to the forum from my iPhone or I'd show it. But if u google a picture of the 5.7 96-98 vortex you can see the line on the passenger side. It goes from the valve cover to the near end of the intake, close to the silencer box area on top of throttle body.

 

[The_Nuke]

The passenger side line connecting the valve cover to the TB is the PCV line. Is that the one you spliced the CC into?

The line should connect to the valve cover by way if the PCV valve. The line will plug into the PCV valve which plugs into the valve cover. If you pull that PCV valve out of the valve cover and leave the line to the TB attached, there should be a vacuum on that line which is evident by putting your thumb against the PCV valve opening. The vacuum will suck your thumb up to it and resist you pulling it away.

You would not be able to feel the reversal of air flow at max torque by removing that valve, nor would you want to try I don't think. Since the engine has to be operating at maximum load, redline in other words, you would have to be lean over into the engine bay with your arm laying across the engine while trying to replicate that. That would be unpleasant with the engine screaming at 5-6K RPMs next to you IMHO.

Nevertheless, if you are getting buildup inside the intake manifold and on the backside of the throttle body, then it is coming through the PCV line (and PCV valve). That is the only line that connects the crankcase to the intake manifold.

NOTE: Oily sludge inside the intake manifold and on the backside of the TB is the expected result of having a functioning PCV valve and PCV line.

The fresh air line connects the crankcase to the air box (or air intake tube). Any oily buildup coming from there would be most visible right at the connection point on the air box or intake tube. There could be some buildup on the front side of the throttle body, but it would be much less evident than the buidup upstream at the connection point, and honestly I would be very surprised and worried if there was enough to be seen on the front side of the TB.

NOTE: Oily sludge inside the air filter box, on the backside of the air filter, and/or on the inside of the air intake tube is not an expected result of having a functioning fresh air line. That only happens when the fresh air line reverses it's flow of air, and that only happens when the engine is operating at WOT and more specifically when it is producing maximum torque. So out of all the time spent at WOT, this reversal of flow in the fresh air line will only happen for a small portion of that time...maybe a second or two at the most (unless drag racing or something similarly WOT intensive).

Given all that, it sounds to me like you mistook your fresh air line for the PCV line, and installed the CC on that. That would explain the lack of any oily collections in the CC. It would also explain the oily buidup inside the intake you reference since intake manifold deposits have to be coming from the PCV line and cannot come thru the fresh air line (because it does not connect to the intake manifold).

 

[Serolim]

The line CC is in is the fresh air line, the valve line is on the driver side, I routinely change that valve every 15k or so as it's like 3-5 bucks. This like I speak of, has no valve, just a hard line with a soft elbow to the top of air intake after the filter but on the end of the tube befor TB.

 

[Rhymingmechanic]

It sounds like your catch can solved the problem of excessive blowby putting oil mist into the intake duct.

The PCV system removes blowby by pulling clean air through the crankcase. PCV flow, when the valve is open, is like this: fresh air line after the engine air filter>crankcase>PCV valve>throttle body. As the engine wears, more blowby gets past the rings. That makes crankcase pressure vent backwards into the fresh air side under some conditions.

In the carburetor days, the fresh air tube was connected to a little filter pad inside the round air cleaner housing. This often led to oil mist soaking the air filter element on high-mileage engines. When hot rodders replaced the stock air cleaner with an open element and a breather on the valve cover, they got to enjoy the odor of blowby inside the cabin at wide-open throttle.

 

[Serolim]

Originally Posted by Rhymingmechanic
It sounds like your catch can solved the problem of excessive blowby putting oil mist into the intake duct.

The PCV system removes blowby by pulling clean air through the crankcase. PCV flow, when the valve is open, is like this: fresh air line after the engine air filter>crankcase>PCV valve>throttle body. As the engine wears, more blowby gets past the rings. That makes crankcase pressure vent backwards into the fresh air side under some conditions.

In the carburetor days, the fresh air tube was connected to a little filter pad inside the round air cleaner housing. This often led to oil mist soaking the air filter element on high-mileage engines. When hot rodders replaced the stock air cleaner with an open element and a breather on the valve cover, they got to enjoy the odor of blowby inside the cabin at wide-open throttle.


So nothing to be concerned about then, thank you. Seems the longer hose solved it, very little almost nothing makes it to the CC in 500miles, tho in addition to length about 3feet longer, it also went to a 3/4th instead of a 1/2. Not sure that matters much or not.

Since I'm getting blowby from my fresh air, I assume catch-caning the pcv tube would also be in order? Oil loss is maybe half a quart at 5k miles. If that. ~ I was really only worried about oil inside my intake, I'm sure my injectors are keeping the valves clean.

 

[Rhymingmechanic]

Most of the catch can discussions on here are about keeping oil out of the PCV. Your consumption doesn't sound bad, though. I wouldn't make the effort unless it was ingesting a lot of oil.

It may not be correct, but my assumption is that a larger diameter clean-air tube wouldn't make a difference since flow is regulated by the PCV valve.