PCV Valve Replacement with Pictures

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Den49, Jun 25, 2015.

  1. Rocky Mountain Priusman

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    Had a look at the valve today. It certainly does have something applied inside the threads. I'll trust that they added their special sauce and install it at 15 ft/lbs.
     
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  2. mikey_t

    mikey_t Active Member

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    I think mine needs to be replaced as my oil burning has picked up again. If working from the top and removing the intake manifold, do any coolant lines need to be removed? It's been a while since I've worked under the hood.
     
  3. Ed Beaty

    Ed Beaty Active Member

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    From NutzAboutBolts:
     
  4. mikey_t

    mikey_t Active Member

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    I've watched his video. I can't get under my car to work on it so I'd rather go from the top.
     
  5. Ed Beaty

    Ed Beaty Active Member

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    Pretty sure you must remove the intake manifold to get at it from the top, so the NutzAboutBolts EGR video is the thing.
     
  6. mikey_t

    mikey_t Active Member

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    Yeah I can revisit that one. I just thought someone might know and have tips before I scrub through the video later. I remember that the throttle body had coolant hoses attached and that it could just be pulled aside rather than detached from the hoses, but I forget if the IM had any.
     
    #66 mikey_t, Apr 6, 2021
    Last edited: Apr 6, 2021
  7. PriusII&C

    PriusII&C Member

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    I have never replaced the PCV valve personally. But a few people (such as @Mendel Leisk) have stated on PC that the coolant lines don't have to be disconnected.
     
    #67 PriusII&C, Apr 6, 2021
    Last edited: Apr 6, 2021
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  8. Mendel Leisk

    Mendel Leisk Senior Member

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    If any way possible, I’d go from below. From above its maybe possible without intake manifold removal, but VERY awkward to reach. And yeah, you can leave coolant hoses connected to throttle body, and that’s the only ones you have to deal with.
     
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  9. mikey_t

    mikey_t Active Member

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    OK great, thanks. I dont mind taking off the IM, I should probably replace the gasket anyway. But since it's harder to do car work at my apartment in general, dealing with coolant would have added a bunch of extra things to deal with.
     
  10. AW82

    AW82 Member

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    Yes, I can confirm that you can leave coolant hoses attached to the throttle body and remove the manifold. I also believe you can remove the pcv valve without removing the intake manifold. I didn't try it, but it's not that buried. Especially if you have a long socket extension and a socket "knuckle." Just remove the airbox and reach behind the manifold.
     
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  11. mikey_t

    mikey_t Active Member

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    Is there any way to tell if the PCV valve is clogged or worn? I've just removed mine and the inside part doesn't seem any looser or tighter than the new one if I shake it around.
     
  12. ASRDogman

    ASRDogman Senior Member

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    They are less than $10. Since you already have it out, good idea to replace it.
    If it was easy to get to, clean it and put it back in. I should shake losely. But you can't really tell
    if it's okay or not.

     
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  13. mikey_t

    mikey_t Active Member

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    OK, thanks. The new one is on and the intake manifold is being cleaned again. It's getting a new gasket too.
     
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  14. rjparker

    rjparker Senior Member

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    It is a simple check valve. One direction it allows air flow, the other direction it blocks air flow. Clogged open or shut is bad.
     
  15. ASRDogman

    ASRDogman Senior Member

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    Clean those egr ports good! (y)

     
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  16. mikey_t

    mikey_t Active Member

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    Any idea if I can drop this off at a scrap metal yard for recycling or if it's just waste now?
     
  17. ChapmanF

    ChapmanF Senior Member

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    A PCV valve is one of those deceptive things where a pretty complicated job is being done by a simple-looking arrangement of a pintle and a couple springs, but there's a lot of crazy black-magic behind the exact rates of those springs and the exact machined shape of that pintle, selected by people who know the exact blow-by characteristics of a particular engine and do hairy fluid-dynamics in their sleep. It's sort like what's needed to design a carburetor, another one of those deceptively simple kinds of things.

    Part of the fun of building a PCV valve is getting it to do physics backwards. Normally the harder you suck on something, the more flow you get. But engine manifold vacuum is highest when the engine is doing the least work. A PCV valve needs to flow less when the vacuum increases; it has to behave all of these different ways under different engine operating conditions:

    pcv4.png

    The trick is to build something out of a pintle and two springs and have its flow-vs-vacuum curve come out as close as possible to the engine's blowby-vs-vacuum curve:

    pcvc.png

    Here the surprising thing isn't that the curves don't quite perfectly match, it's that anybody was able to get them that close using such a "simple" device.

    But it ends up being that the "simple" device (when it's the exact part number listed in the manufacturer parts catalog for the exact engine) has its few "simple" parts very very tailored to that application; that's why Toyota warns against replacements from some aftermarket supplier that might have a much smaller number of orderable parts and cross-reference them to a large number of engines. If the one that came in the engine isn't bad, it is possible to achieve worseness by replacing it.
     
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  18. Mendel Leisk

    Mendel Leisk Senior Member

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    Moral of the story: get the OEM. Its $10 at most.
     
  19. wheezyglider

    wheezyglider Active Member

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    Heh. I do enjoy the seminar when it fits in browser page or two. Kinda wondering if the hybrid application (not so much the Atkinson cycle but more the different way the engine gets loaded) causes us to dwell more in a particular part of that curve than a conventional ICE.
     
  20. mikey_t

    mikey_t Active Member

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    Literally $10.01 with tax from amazon :LOL:
     
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