What's this tube for? PCV line?

Discussion in 'Gen 3 Prius Main Forum' started by Tekken, Apr 13, 2022.

  1. Tekken

    Tekken Member

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    Hello, is anyone can tell what's that tube for? I circled on my picture. Is it same as PCV line to release engine pressure?
    I forgot to connect it back when I check the oil trap under throttle body. It didn't give me check engine light. But it has no power when i was the highway. Even at 3000 rpm

    20220412_220628~2.jpg
     
  2. xliderider

    xliderider Senior Member

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    No, that's not the PCV valve hose. The PVC hose is down lower on the crankcase. It connects directly to the intake manifold, after the throttle body.

    That's probably a valve cover breather hose.

    Reconnect the hose and take it for a test drive.

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  3. xliderider

    xliderider Senior Member

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    Here's what the Prius Gen 3 PCV hose looks like, it's the U-shaped hose on the left in this picture. 20210910_115744.jpeg

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  4. burebista

    burebista Member

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    Yep, that's the one pictured in my engine bay when I did that IM cleaning.
    [​IMG]
     
  5. xliderider

    xliderider Senior Member

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    Here's my picture... without the hose.

    20210910_123839.jpeg

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  6. Mendel Leisk

    Mendel Leisk Underfoot

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    I wonder if that hose is tied into PCV system though; on gen 2 a hose like that has the pcv valve at the valve cover end.
     
  7. ChapmanF

    ChapmanF Senior Member

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    Oh, it's definitely part of the PCV system; it's the breather hose shown at the top of this picture. It connects between the intake upstream of the throttle body and the valve cover.

    Next down, the picture shows the other PCV hose, the little U shaped one, that connects between the manifold downstream of the throttle body and the PCV valve.

    Flows in the breather hose can be either direction depending on circumstances. In times of high manifold vacuum, low throttle opening, the breather supplies fresh air into the valve cover, helping to scavenge out the blow-by gases through the PCV hose. In high-load operation, both the PCV hose and the breather hose are pulling gases out of the engine.

    [​IMG]
     
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  8. PriusCamper

    PriusCamper Senior Member

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    Thanks for helping us understand this... I was fairly certain it was part of the PCV system...

    A couple questions:

    1) Can this ever foul the air intake with oil if things go wrong?

    2) Is this something Gen3 added than Gen2 doesn't have? Or same thing in both just different location?
     
  9. ChapmanF

    ChapmanF Senior Member

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    The two hoses are pretty much the standard arrangement on anything I've worked on (other than a friend's 1965 pre-PCV Ford, which just had a filtered breather oil cap and a draft tube sending the yuck straight into the surrounding wind).

    In the 1NZ engine, the two hoses run side-by-side.

    [​IMG]
     
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  10. Tekken

    Tekken Member

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    Thanks guys.. That's what I thought, it has a similar or same function as PCV line help to release pressure from the Engine. The positive point of this line that it has not release any Oil Vapor as PCV line on the bottom

    Now, it bring to point that can we further restrict PCV line on bottom out put to eliminate OIL Vapor to manifold and while letting this line to do their PCV job??
     
  11. Tekken

    Tekken Member

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    double posted
     
    #11 Tekken, Apr 14, 2022
    Last edited: Apr 14, 2022
  12. Mendel Leisk

    Mendel Leisk Underfoot

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    That's the 2nd gen engine?

    My hunch: it's better/safer to install and maintain an oil catch can in along the lower PCV line.
     
  13. ChapmanF

    ChapmanF Senior Member

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    1st gen, 2nd gen, and c.
     
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  14. PriusCamper

    PriusCamper Senior Member

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    That's because he was explaining the difference between Gen2 and Gen3...
     
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  15. Paladain55

    Paladain55 Junior Member

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    You would actually want to do the opposite. But leave it alone or put a catch can on.
    (LS motors with undersized PCV systems push oil, but when you increase the size of the line it reduces the pressure and reduces the amount of oil they push through the PCV line into the intake)
     
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