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 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 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 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. :)
     
    Raytheeagle likes this.
  9. PriusII&C

    PriusII&C 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
     
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