PCV Valve and Oil Consumption???

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Timjor, Mar 23, 2016.

  1. Timjor

    Timjor New Member

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    Dealer just told me I had low oil when I dropped it off, which was "potentially" caused by a clogged PCV. Can someone explain if this would be the case? Also, I saw the part is relatively cheap - is it hard to replace? I have done some major work on older cars, but these new "computerized" cars are a little more tricky.....
     
  2. JC91006

    JC91006 Senior Member

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    You can try changing the PCV valve but I don't think that'll resolve the oil burning in your 2004 Prius. Older Prius cars have a history of burning oil, just keep a close eye on it and keep it topped off.
     
  3. andrewclaus

    andrewclaus Active Member

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    Yeah, the PCV change is a "Hail Mary." It's easy enough to do--as I remember you have to dismount the relay block.
     
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  4. edthefox5

    edthefox5 Senior Member

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    PCV valve is the same valve used way before "computerized" cars. It vents the crankcase so the seals don't blow out. Like most modern cars its vented into the throttle body which has a major drawback in that alot of gunk is dumped into the tb.

    Your new and welcome to you. Now the bad news. That valve is not causing your oil loss. Its the oil rings on the pistons are worn out and now you have alot of blowby. You did not mention miles so at your age I surmise 200K+ miles on your car.

    Oil loss is greatly exacerbated by running the engine low on oil. Many many posts here about folks who have allowed the oil to run so low the check engine light came on. This event alone will damage the oil rings and alot of times damage the lower end bearing assy also as that assy is serviced by sling lubrication. if the oil is low below the sling line no lubrication. No sling affect's the rings, the piston cylinder walls, and the piston wrist pin assy first as they are the highest oil serviced components.
    if your car has seen that engine light low oil event don't put any money into the car. Even if it hasn't don't put any money in the car. Keep vigilant eye on the oil and keep it at the full line at all times and drive it till it explodes.
     
    #4 edthefox5, Mar 23, 2016
    Last edited: Mar 24, 2016
  5. James Luckett

    James Luckett Junior Member

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    It could be the PCV. Probably not, but possibly yes and it would be great news for you it if were. It's worth the small cost of replacing it in the off chance that will fix it. PCVs do fail. When they fail, oil consumption can go way up as a result. They are cheap. So, no reason to assume the worst, just because the worst is the more likely scenario.
     
  6. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    If you DIY the change (or removal for cleaning): do not use an open-ended box wrench to brake it loose. It's tempting to do so, because without pulling off the hose it's the only wrench you can use. But get the hose off first, then use either a deep socket on a ratchet wrench (long-handled makes it easy) or a closed-end box wrench.

    The issue with open-end box wrench is the jaws have increasing thickness, and when you breake the PCV valve loose the wrench can slam down, end up punching a hole in the valve cover.

    If you're determined to use open-end box wrench (it is convenient), put some sort of gauge plate over the valve cover, and take it real easy with the wrench.

    FWIW, just removing the valve and giving it a few shots of carb cleaner, it's likely good-as-new. OTOH, they are cheap, $5~10 at most.

    If you are reusing the PCV valve, or the new one has no sealant on the threads, clean and dry the threads (both sides of the connection) with a little brake cleaner (don't spray into the valve cover orifice, just spray a little on a brush), then apply a ring of Permatex ThreadLock 243 (medium duty, effective even with slight oil residue), to the PCV valve threads, about mid-way along the length. Torque value is 20 ft/lbs.
     

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    #6 Mendel Leisk, Jan 17, 2020
    Last edited: Jan 17, 2020
  7. BLNT

    BLNT Junior Member

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    I replaced the PCV valve on one of our Gen2 but the oil consumption remained. Maybe you can try an engine additive made by BG products I heard good things about from a guest I had on. I'm also looking to order one for our 2004 Prius to try.
     
  8. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    A pro mechanic inexperienced with 2nd gen Prius might make the same screw up. Would be good to caution them in advance, and check the valve cover after.
     
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