What is this hose?

CARJACKED · Oct 3, 2005

Drivers side, upper intake, toward the rear...There is a tube coming out of the (stock) intake and leading down towards the middle of the lower intake. It is covered with oil...
What the hell is this?
Can I delete it?
I dont seem to remember this being there on my fox, or is it just me?

1105 · Oct 3, 2005

Its the hose for the PCV valve. I would not delete it unless you have another way to vent the crankcase pressure. You might just need a new PCV valve.

95Vert · Oct 3, 2005

There should be 2 coming from behind going into the pcv valve. DO NOT DELETE. Put a filter in between the lines to catch the excess oil.

CARJACKED · Oct 3, 2005

If this is serving as crankcase ventilation, why do we need the hose going from the oil fill tower to the air intake for positive crankcase ventilation...can I delete that?

I want to delete more ****!!!

1105 · Oct 3, 2005

the more ventilation the better. Do whatever you want though. Take the line off of the air intake and stick a breather cap on the filler neck. Plug the hole in the lower intake for the PCV valve and the fitting on the intake for the hose.

The more your car can vent the pressure the better but I doubt you'll see any negative side effects by deleting the PCV as long as you run the breather on your valve cover.

a50sn95 · Oct 3, 2005

NO, that's where the air ENTERS the crankcase, goes through the engine and then through the PCV valve to the combustion chamber. It comes from there so it is included in the air MEASURED by the MAF. If you put a vented cap on your valve cover, and leave the PCV, you are allowing unmetered air in, which spells LEAN....

MysteryMachine · Oct 4, 2005

i have a vented cap and have no problems car runs great

Green 94 5.0 · Oct 4, 2005

as people already said, the only way to eliminate the pcv is to add a breather to the oil fill tube. the thing is, to do that properly, you need to add a breather to BOTH valve covers.

94opalgt · Oct 4, 2005

i have a k&n breather on my valve cover with no problems also.hey carjacked,if you oil dripping off that hose can you imagine what the inside of your intake looks like?when i took the stocker off of mine it was caked with oil.the upper and lower,the runners in the stock heads even my headers were coated with oil.the tops of the pistons too.im running a steeda oil separator now with no oil problems in the intake.

CARJACKED · Oct 4, 2005

a50sn95 said:
NO, that's where the air ENTERS the crankcase, goes through the engine and then through the PCV valve to the combustion chamber. It comes from there so it is included in the air MEASURED by the MAF. If you put a vented cap on your valve cover, and leave the PCV, you are allowing unmetered air in, which spells LEAN....

Why do I have oil in my air intake tube and throttle body then? If the air was moving into the crankcase it seems like it would prevent that...

MysteryMachine · Oct 4, 2005

maybe the way i did mine is ok? only hose i got rid of was the one going from the cai to the valve cover i still have all that other stuff

yellowstang1994 · Oct 4, 2005

CARJACKED said:
Why do I have oil in my air intake tube and throttle body then? If the air was moving into the crankcase it seems like it would prevent that...

What I always thought was the pcv valve ventilates the crank case by allowing it to re-enter the air through the intake and re-use it. But in doing this oil gets sucked up with the air and gets thrown back in your intake. The best thing to do is run an oil separator. I just did this last weekend. You can make one yourself for under $20. Theres some threads around here about it still.

a50sn95 · Oct 4, 2005

CARJACKED said:
Why do I have oil in my air intake tube and throttle body then? If the air was moving into the crankcase it seems like it would prevent that...

I think you mis-understood my explanation.
Let's go backwards.
Upper intake manifold is under vacuum when the engine is running.
Hose from upper intake to PCV valve is SUCKING air from the crankcase. (And sometimes will suck oil too, since it's SUCKING that air from the lifer valley. This is why you have oil in your hose and upper intake, like most of us do. I have an oil seperator in my PCV hose, as someone here has already suggested.)
The air IN the crankcase HAS to come from somewhere. Since the crankcase is SEALED from the factory, it would PULL through gaskets or seals unless there was somewhere else for it to come from.
So, Ford put that hose from the Oil fill tube to the Air intake tube to allow FILTERED air into the crankcase. AND, since it is entering the upper intake through the PCV valve, it is going to the combustion chamber to get burned and sent out the exhaust. This is the same basic design since the 60's, with the ADDITION of pulling the air AFTER the Mass Air Meter, so the air going through the crankcase can be measured as well. Didn't matter when we had carbs, cause you just adjusted you carb for it. Since we are fuel injected, it is WISE to allow the system to measure all the air entering the intake manifold, or a lean condition could result. Modern systems CAN adjust for it (thats what the keep alive memory is for in our computers), but bypassing the hose on the valve cover to the air tube IS allowing unmetered air to enter the engine.
I hope this clears up any confusion, and understand there was a logical reason for FORD to put that hose there in the first place.

CARJACKED · Oct 4, 2005

I have a catch can (oil seperator) on the camaro for the pcv system, so I could make one without any problem. It just seems rediculous to put one on the hose going to the valve cover when I could just do a breather cap. i might put one on the hose going to the upper plenum though...

a50sn95 · Oct 4, 2005

CARJACKED said:
Why do I have oil in my air intake tube and throttle body then? If the air was moving into the crankcase it seems like it would prevent that...

I see why my first answer was confusing, I was answering this question:

CARJACKED said:
If this is serving as crankcase ventilation, why do we need the hose going from the oil fill tower to the air intake for positive crankcase ventilation...can I delete that?

Make sense now?

a50sn95 · Oct 4, 2005

CARJACKED said:
I have a catch can (oil seperator) on the camaro for the pcv system, so I could make one without any problem. It just seems rediculous to put one on the hose going to the valve cover when I could just do a breather cap. i might put one on the hose going to the upper plenum though...

That's where is goes. The hose to the valve cover is just letting air into the crankcase. The hose from the PCV is the one that sucks up oil mixed with the air....
Here's what I used, mounted on the firewall right above the PCV hose....

18mustangs · Oct 4, 2005

a50sn95 said:
NO, that's where the air ENTERS the crankcase, goes through the engine and then through the PCV valve to the combustion chamber. It comes from there so it is included in the air MEASURED by the MAF. If you put a vented cap on your valve cover, and leave the PCV, you are allowing unmetered air in, which spells LEAN....

Your darn right!

GRGT1994 · Oct 4, 2005

a50sn95 said:
. . . The air IN the crankcase HAS to come from somewhere. Since the crankcase is SEALED from the factory, it would PULL through gaskets or seals unless there was somewhere else for it to come from.
So, Ford put that hose from the Oil fill tube to the Air intake tube to allow FILTERED air into the crankcase. . . .
I hope this clears up any confusion, and understand there was a logical reason for FORD to put that hose there in the first place.

Actually, I'm more confused. Though I'm sure you know more about this than I, so help me out here.

The engine sucks air into the intake manifold, through the TB, CAI, MAF and filter. It's not just passively breathing in air. It aggressively draws air in (vacuum).

This suction would draw air from any pathway available. Any opening or crack in the intake tube, hole cut in the filter, or more importantly (for this topic) the tube from the filler neck to the intake tube would yield air to this suction. In other words, air flows from the valve cover, through the filler neck tube, and into the CAI tube. I can't see how air would possibly flow in any other direction here (unless vacuum in the passenger side valve cover is phenominal - and even if it were, wouldn't this lean the passenger side out compared to the driver's side?). But as I read your explanation, it seems that you are describing the opposite.

I am not trying to call you out, just trying to understand what actually is going on with this portion of the engine. (BTW, after my HCI install I left my filler neck tube drawing air from a long tube feeding from the fenderwell. I guess I didn't give any thought to the filtration and metering issues you mention. So tonight I went ahead and hooked it up to the CAI tube. But I had no CEL or driveability issues as it was set up.)

Any thoughts?

a50sn95 · Oct 4, 2005

No Prob. I DO believe I have a clear understanding, but explaining it isn't quite that easy.
There is no (comparable) vacuum on that side of the throttle plate with the throttle closed. At idle, the is more vacuum on the intake side of the TB, than on the filter side of the TB. So, air is actually travelling the path I described.
Further, even with the throttle open, there is no other place for air to ENTER the crankcase. If you are going to pull air through the tube on the valve cover, where is the air going to come from? The PCV valve is drawing from the crankcase, and the only path INTO the crankcase is through the air filter. Everything else is sealed up. So, when the throttle is open, the PCV system is just not as effective, as there is more vacuum in the tube to the TB. Still, if you put a guage on each side of the TB, you'l still have more vacuum on the engine side, so the PCV system would still draw through the tube on the V/C.
Take a tin can, poke a hole at each end, and suck through one of the hole. The other hole is where the air comes in. Same in the engine.
As far as leaing out one side versus the other, that is not how it works. The crankcase is seperate from the combustion chamber. the PCV is drawing air from the crankcase, into the intake to go to the combuston chamber. The combustion chamber is creating the vacuum in the intake. They are seald from the crankcase by the piston rings. That is what blow-by is. Combustion chamber air getting past the rings into the crankcase. It leans out the engine because the air ENTERING the intake through the PCV valve is no getting measured by the MAF, if you just put a breather cap on the valve cover.

Here's a short description:
http://www.lapelec.co.uk/PCV.htm
Another Thread:
http://forums.stangnet.com/showthread.php?t=516650
And Another:
http://forums.stangnet.com/showthread.php?t=510093
Dennis

GRGT1994 · Oct 5, 2005

Thanks for trying again, but unfortunately I got only more confused. So I Googled it. I found two links that are particularily helpful. This one. And this one.

As it turns out, it appears that air flows in both directions through that tube between the oil filler neck and the CAI. It all depends on engine load, blowby and vacuum. So we were both right.

What is this hose?

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