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Ford Focus SE Sport 2003
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Discussion Starter · #1 ·
Yesterday I replaced the air filter on my Zetec 2003 Focus. When I removed the filter, I noticed a small piece of square sponge at the bottom of the filter leading to a small hose that seems to be going right inside the valve cover. Since the sponge was rotting I replaced it with another one that I took from my lawn tractor (I cut it to fit it in the Focus).

What is the purpose of that little hose? It can be seen in the attached picture.

Hood Motor vehicle Vehicle Car Automotive exterior
 

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2004 ZX3 SVT EE 173k miles. 2004 ZX3 SVT 194k miles
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That is part of the crankcase ventilation system. PCV is another part. The sponge is to keep any oil off the air filter. Good job seeing it and replacing it. Most are missing that I see.
 

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I replaced it with another one that I took from my lawn tractor (I cut it to fit it in the Focus).
www.rockauto.com/en/moreinfo.php?pk=383432&cc=1385524&pt=4932&jsn=734

Quantity 1 is a box of them. A dozen or so in the box.

So the air flow is from the box to the crankcase or vice versa?
PCV system hose from valve cover to intake acts as an air intake most of the time
www.focusfanatics.com/threads/zetec-engine-mystery.565690/#post-8430202

I heard it can vent too, when needed.
 

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Discussion Starter · #5 ·
www.rockauto.com/en/moreinfo.php?pk=383432&cc=1385524&pt=4932&jsn=734

Quantity 1 is a box of them. A dozen or so in the box.



PCV system hose from valve cover to intake acts as an air intake most of the time
www.focusfanatics.com/threads/zetec-engine-mystery.565690/#post-8430202

I heard it can vent too, when needed.
Ha, so it can be both ways. I’ll order some but I’m sure the one I installed is just fine. Just in case I put a drop of oil on it.

Also, and I found that strange, there was a bit of sand at the bottom of the box but it was all sticky. Had to use a little brush and a vacuum to pick it up.
 

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Discussion Starter · #11 ·
If the foam is for preventing oil to travel to the air filter, I deducted that the flow was coming from the valve cover. And I didn’t see a valve so these two parts are directly connected one to another.

That‘s why I asked for the precision.
 

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Breather

In order for the PCV system to draw fumes out of the crankcase, the system must have a source of fresh air. The source of this fresh air is the "crankcase breather", which is usually ducted from the engine's air filter or intake manifold. The breather is usually provided with baffles and filters to prevent oil mist and vapour from fouling the air filter.

 

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Breather

In order for the PCV system to draw fumes out of the crankcase, the system must have a source of fresh air. The source of this fresh air is the "crankcase breather", which is usually ducted from the engine's air filter or intake manifold. The breather is usually provided with baffles and filters to prevent oil mist and vapour from fouling the air filter.

Maybe so. If it only flowed from the airbox to the valve cover, the foam wouldn't get saturated with oil. That being said, the pcv system has to get air from somewhere. Too tired to think today
 

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Discussion Starter · #16 ·
Maybe so. If it only flowed from the airbox to the valve cover, the foam wouldn't get saturated with oil. That being said, the pcv system has to get air from somewhere. Too tired to think today
Well, my piece of foam was 20 years old. It was decomposing and oily but the oil coming from there must be really minimal because otherwise, the bottom of the air filter box would have been oily, which wasn’t the case. I think you could get away without the foam but the air filter would wear (just a bit) faster.
 

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the pcv system has to get air from somewhere
It can exhale too. Like breathing:

what if blow-by pressure, builds up faster than the PCV valve system can handle it? The excess pressure, flows back through the breather hose, to the air cleaner.

dannysengineportal.com/pcv-valve-system-pcv-positive-crankcase-ventilation-system/
 

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Discussion Starter · #18 ·
It can exhale too. Like breathing:

what if blow-by pressure, builds up faster than the PCV valve system can handle it? The excess pressure, flows back through the breather hose, to the air cleaner.

dannysengineportal.com/pcv-valve-system-pcv-positive-crankcase-ventilation-system/
Now you lost me completely! I’ll stick with knowing about the small piece of foam!
 

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Discussion Starter · #20 ·
The link may help. Good info about the PCV valve system.
Yes, maybe. My mechanics friend says he is starting to learn from me about technical details. He sure knows how to replace a part but he took his retirement because he didn’t want to learn the new electronics of newer cars. He only fixes older car for friends part time, especially that he has a bad back too, like me.
 
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