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Question about oil on top of the valve cover

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Joe Flies, Dec 21, 2021.

  1. Joe Flies

    Joe Flies Junior Member

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    I have a used gen2 with 180k miles. I'm losing about a quart of oil every 1000 miles which I have been just dealing with by topping it off. I have found oil in the throttle body and already replaced the PCV.

    I don't see obvious leakage below the valve cover gasket and I don't see oil on my garage floor. I do see oil residue on the top of the valve cover, accumulating around where the top of the coilpacks are.

    Even though I don't see oil on the valve cover gasket, I was going to go ahead and do it anyways. Should I be buying any other replacement parts while I'm at it? Like I am not sure if I need to buy replacement coilpacks or other parts I should buy before I take it apart again.
     
  2. JC91006

    JC91006 Senior Member

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    So you want to take the valve cover off, give it a good cleaning and put it back with a new gasket? That'll look better but still won't do much for the oil burning
     
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  3. Joe Flies

    Joe Flies Junior Member

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    Sorry, I should have stated my question a different way - what would cause oil to appear on the top of the valve cover?
     
  4. Fred_H

    Fred_H Misoversimplifier

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    Off the top of my head, I can think of three possible causes:

    1. Oil was once spilled on top of the valve cover or blown up from somewhere else like the PCV fittings or hoses.

    2. There are valve cover gaskets (or O-rings?) around the bottom of each of the spark plug wells, one (or more) of which could be leaking.

    3. A spark plug could be loose, have a faulty crush washer, or the insulator could be cracked. (Even if the spark plug well is not full of oil, the hot oil fumes leaking past the spark plug and through the ignition coil seal can condense onto the cooler external surface of the valve cover.)

    I would start by removing the ignition coils to see if it is obviously coming from one of the spark plug wells. If it is, then I would remove the spark plug, thoroughly clean the surface where the crush washer seats on the cylinder head, and replace it with a new OEM or top quality plug. Then check it again after a few thousand miles.
     
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  5. SFO

    SFO Senior Member

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    If removing the plugs, you might consider doing a "piston soak".

    FYI : you're moderated until you've posted 5 times.
     
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  6. JC91006

    JC91006 Senior Member

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    I would think if it's on TOP of the valve cover, it would just be spilled oil, careless people adding oil to the car
     
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  7. Fred_H

    Fred_H Misoversimplifier

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    That's right, I was just assuming without good reason that he already tried cleaning it up, but it appeared again. But he didn't actually say that. So you're right, that would be the first thing to check.
    ---------------------------------
    By the way, Joe:
    This is normal and harmless. You probably already knew, but just in case, and for other readers of this thread.
     
  8. Joe Flies

    Joe Flies Junior Member

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    Thank you everyone for the advice, I will start chasing down the gremlins. I used to tell my wife that it was boring to have a prius because I never had to take it apart to get to work, this is really the first time I've had to do anything but the most basic stuff.
     
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  9. edthefox5

    edthefox5 Senior Member

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    Might as well change the sparkplugs too. And the coil on plugs may be damaged from oil leaking into the spark plug well from a failed gasket.I saw oil leaking into my spark plug wells at 120,000 miles. I replaced all the cops then with new oem cops. There $100 each online Olathe Toyota. I had bought one every few months for this job.
    When you take the cop off use your iPhone and take a picture of the plug in the well see if any oil is leaking into the well like in my picture.

    Go to the dealer or buy Toyota part only buy and a new valve cover gasket. Its a whole deal to get the cover off and replace the gasket you will need to take the windshield wipers off and windshield water dam valley off to get to the back bolts. See my pictures.

    Which is a very good thing to do because if the car lives outside the dam will be pretty clogged with leaves. After you take out all the debris out of the dam get a garden hose and hose out both ends should see a very steady stream behind both front tires thats the dam water dump.

    But like JC says I doubt that's your issue its just the engine eating oil which is very very common on a G2. But cant hurt to replace the gasket.

    last thing where the timing cover meets the block put a little black form a gasket at that junction then put the gasket on.

    Good Luck!
     

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  10. ttou68

    ttou68 Active Member

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    Without any photo it's hard to tell exact location or direction of the source...
    I have seen failed oil cap gasket cause oil leak to the valve cover.. mostly around the area of oil cap..

    Posted via the PriusChat mobile app.
     
    #10 ttou68, Dec 23, 2021
    Last edited: Dec 23, 2021
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