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OCC and PCV Valve Relocation, Will it Work?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by PriusII&C, Mar 25, 2021.

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  1. PriusII&C

    PriusII&C Active Member

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    Inspired by a YouTube video, I wonder if we can do the following to combine OCC and PCV valve relocation. If this works, it will kill two birds with one stone: reduce oil going to the throttle body / intake manifold, and move the PCV valve far away from the crankcase. It also allows future PCV valve replacement much easier. The beauty is it does not require extra work, just as much as installing an OCC.

    The process is very simple. Just swap the PCV valve with the OCC outlet fitting:

    1. OCC fitting (M16x1.5 / 10mm) to crankcase PCV female thread.
    2. 3/8" hose to OCC inlet fitting.
    3. PCV valve as OCC outlet fitting.
    4. 3/8" hose to 3/8" coupler.
    5. Original PCV hose.

    The concern I have is: will this add additional oil to the OCC? Since the pressure inside the OCC will be the same as in the crankcase, will extra oil be collected when the PCV valve is (almost) closed such as at idle, or even when car is turned off but engine is hot (such as in summer)?

    Please share your comments.
     
  2. AW82

    AW82 Member

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    Pressure in the OCC? No. At idle, OCC will be in vacuum. As I understand it, with the way the valve works, the only time the pressure (or lack thereof) will be the same in the crankcase and in the OCC will be when the engine is under high load.

    But I think your question is whether moving the PCV will make extra oil be collected in the OCC when the engine is off (not that it will make additional oil vapors leave the crankcase), right? (Because of vacuum, I don't think moving the PCV will have an effect during idle). For that, I think it depends on A) whether a cooler PCV further from the crankcase will flow less when the engine is off and B) what the orientation of the PCV is since, as I mentioned in another thread, a vertical PCV appears to close more fully than a horizontal PCV when the engine is off.
     
  3. Mendel Leisk

    Mendel Leisk Senior Member

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  4. PriusII&C

    PriusII&C Active Member

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    As far as the orientation of the PCV valve, it stays the same either in the stock position or in the OCC fitting.
     
  5. PriusII&C

    PriusII&C Active Member

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    True, it can be done from below, with some hard work though.

    I am still debating about an OCC for my car during the soon-to-be DIY. On one hand, it probably will reduce oil burning and EGR clogging, on the other hand it can be a potential emission issue for people in California. Judging from a few reports, it only collects around 2 oz per 5,000 miles. Comparing this amount with the typical oil consumption of a middle-aged Prius, it is a small portion. Do you really think an OCC is worth the trouble for a car mostly operated in a warm area like the Bay Area?
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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  7. Grit

    Grit Senior Member

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    define trouble. If emptying it on a regular cycle is trouble then clean egr every 50,000 miles and forego the catch can.
     
    #7 Grit, Mar 26, 2021
    Last edited: Mar 26, 2021
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    I’m not sure ANYTHING will eliminate 3rd gen EGR woes, but OCC “might” slow it a bit.

    And they’re kinda satisfying. :)
     
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  9. PriusII&C

    PriusII&C Active Member

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    By "trouble" I mostly mean the installation: route the hoses, mount the can, ...Probably also remove/reinstall before/after smog check... :p
     
  10. run4priz

    run4priz Junior Member

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    How did this modification work out for you? Considering something similar.
     
  11. Rebound

    Rebound Senior Member

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    I just stumbled on this thread.
    My opinion is that if you’re going to relocate the PCV, the hose from the engine should be routed UP. Otherwise, you’re just draining oil out of your engine.

    It’s proven that an OCC in a Prius will catch goop and it’s goop we don’t want our engines to burn. I installed an OCC in my BMW N55 engine, and it hasn’t collected one drop of oil. But Prius Gen III is a different story.

    I don’t think there’s benefit to relocating the PCV. If anything, it lets more oil out of the crankcase.
     
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  12. xliderider

    xliderider Senior Member

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    I watched that YouTube video, seemed interesting.

    I've installed an OCC down low near the front crossmember, behind the radiator, and relocated the PCV valve to a vertical position, after the OCC and right before going into the intake manifold.

    I used one of the OCC fittings in the original PCV valve location. I don't know if having an "open" port there allows any more oil out than normal since the area involved is so small, less than a square inch. The path then goes down to the catch can, then up to the relocated PCV valve. In theory, any oil vapor that condenses on the tubing walls before reaching the PCV valve will drain down into the catch can.

    It's only been a week since the installation, and I haven't checked how much the oil catch can has collected.

    Here's a picture of the fitting I used to adapt the PCV valve to get a 3/8 inch barb on the input side. There's two because I plan on doing the same thing to our 2014 Corolla with a PCV valve in a similar location on the crankcase as the Prius. 20210811_103350.jpeg

    Posted via the PriusChat mobile app.
     
    #12 xliderider, Aug 27, 2021
    Last edited: Aug 27, 2021
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  13. Rebound

    Rebound Senior Member

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    Guess we’ll see what happens… I’m all ears.
     
  14. xliderider

    xliderider Senior Member

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    Yes, indeed. Ideally, it would be interesting if I could put some kind of baffling on the end, or inside the OCC fitting, to prevent liquid oil that is sprayed onto the small area of the fitting from entering the setup.

    Hopefully, it's not a factor and that all the oil entering the PCV system is in vaporized form.

    Posted via the PriusChat mobile app.
     
  15. xliderider

    xliderider Senior Member

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    I am also concerned about our mandated annual vehicle "safety checks". I don't want to risk failing a safety check and having it documented that I failed due to vehicle modification to a pollution control system.

    Which is why I located the OCC down low and out of sight. It seemed too complicated to route the tubing up from the crankcase, then back down to the oil catch can, then up again to the intake manifold.

    If I do have to go that route, then I have my eye on this.

    Screenshot_20210827-131345_eBay.jpeg

    Posted via the PriusChat mobile app.
     
  16. xliderider

    xliderider Senior Member

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    Also, the OCC shouldn't be a problem for actual emissions on a smog check. Unless you are referring to failing if the inspector sees it and fails you for altering an emissions control system.

    If that is the case, some have proposed taking the OCC out prior to the smog check and using a barbed hose mender to connect the in/out tubes to pass the test.

    Posted via the PriusChat mobile app.
     
  17. Rebound

    Rebound Senior Member

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    I doubt an emissions control guy would notice an OCC, unless it was at the top of the engine bay. They do very fat inspections, they check the ODB, and they check tail pipe emissions. And they aren’t Prius experts, so another hose someplace isn’t going to seem out of place.
     
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  18. Mendel Leisk

    Mendel Leisk Senior Member

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    The original hose costs about $10,
     
  19. xliderider

    xliderider Senior Member

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    Checked the OCC this evening. About a teaspoon of what looks like clean oil in about a week. No sign of water or moisture.

    20210827_201946.jpeg

    Posted via the PriusChat mobile app.
     
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  20. Rebound

    Rebound Senior Member

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    That’s promising!!!
     
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