Burned spark plug ceramic

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Kasra, Nov 18, 2018.

  1. Kasra

    Kasra Junior Member

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    Hi everyone,

    Yesterday, I changed my Gen 3 20181118_160445.jpg transmission fluid and also decided to change my spark plugs as well. I was kinda shocked when I took the plugs out and saw the condition of the spark plugs at 58,000 miles. I understand that these plugs don't have to be changed till 120,000 miles but I just wanted to see how they look.

    Burned ceramic means that combustion gasses are leaking out, right? Why would this happen with only 60K on the plugs? Is this why DENSO replaced these plugs (SC20HR11) with the new model (SC16HR11)? I inspected the spark plugs and applied some of that dielectric grease inside the tube (not on the terminals) before putting it back in.

    What I also noticed was that the plugs were not dry and had oil on them (all 4). I took some pictures that might help. Please let me know what your thoughts are. It's better to prevent a problem than fixing it in the future :)
     

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  2. xerox6135

    xerox6135 Member

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    Mine looked the same at 60,000 miles . I think that is normal for those plugs.

    Posted via the PriusChat mobile app.
     
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  3. dubit

    dubit Senior Member

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    Those plugs look to be in normal condition.
     
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  4. exstudent

    exstudent Senior Member

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    A Zanax or two might help you.

    1) It is NOT burned. Sure the discoloration is concerning, but the car has been functioning normally, right?
    2) If combustion gasses were leaking, you'd be loosing compression, and w/ that power. DTCs would be logged for sure. Think Cause-Effect. No LOSS of compression. No loss in power. NORMAL operation, despite the discoloration.
    upload_2018-11-19_4-0-11.png

    Gen2 service manual does NOT call for dielectric grease. Assuming Gen3 has an identical service procedure, no dielectric grease for you. Undo what you just did: remove the grease.

    More Zanax and counseling.

    What you are seeing is normal. Notice the oil is ON the body (threads), NOT the electrode area (sparking portion) or the upper insulator area. If you see this (pictured below), cause for concern. Also, the car would most likely be running poorly, and DTCs would be logged. Oil on spark plug body-OK. Oil on sparking portion of sparkplug (electrode area), be concerned. If you are really concerned, change out the valve cover gasket and spark plug tube seals.
    upload_2018-11-19_4-25-17.png
     
    #4 exstudent, Nov 19, 2018
    Last edited: Nov 19, 2018
  5. Kasra

    Kasra Junior Member

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    Thanks for taking the time and explaining this :). It originally concerned me due to the fact that this was the condition at 60K miles, not 120K miles (which is what Toyota is recommending). I've done a lot of Spark plugs change and I wasn't sure about the oil on the threads (the well was oil free and dry).

    Again, thanks a lot for everyone that took their time on this post :)
     
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  6. working1

    working1 Active Member

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    plugs.jpg For comparison: After 100K miles on a '12 with 212K miles.
     
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  7. exstudent

    exstudent Senior Member

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    These Irridium plugs are rated for 120K miles by NGK/ND. For the Gen2, Toyota gives two change intervals depending on CARB (150K miles) vs non-CARB state (120K miles).

    The spark plug manufactures base 120K miles on a traditional gas engine, that's ALWAYS ON. The Prius engine is NOT always on.
    Many people have posted pictures of their spark plugs around 120K miles, Plus or Minus some miles, and all the pictures I have seen, the plugs look very good. IMO, you could go longer than 120K miles, but definitely change before 150K miles.

    2007 Prius plugs at 7years, 120,631miles. Left to Right: Cyl1-2-3-4, OLD&NEW. Old plugs were still w/in correct gap of 1.0mm-1.1mm.
    all 4.JPG
     
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  8. Kasra

    Kasra Junior Member

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    Thanks a lot for comparison, should have done the same

    Posted via the PriusChat mobile app.
     
  9. latitude500

    latitude500 New Member

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    Thank you for putting this information on the site, I was freaking out when I pulled out my spark plugs on my 2013 with 121k on it and it looked the same. Good to know it's normal.
     
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  10. Kasra

    Kasra Junior Member

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    1st Topic:

    It's been 2.5 years since I replaced the plugs and I decided to replace the plugs again at 117,328 miles (60,000 miles on the plugs). The reason was a bit roughness when the ICE engaged after each stop and go. I replaced the plugs with NGK ILKAR7B11 which had better laser welding and ground electrode disc ( I just liked the quality better than DENSO SC20HR11). The ICE engages smoothly and I'm happy. That being said, I have a few pictures and questions,

    There are two pictures of the plugs that I pulled out and they look similar to the ones I pulled out two years ago (previous posts). I used a digital endoscope to see what the inside of each cylinder looks like. I would be happy to hear your feedback (sorry about crappy pictures). Cylinder 1 and 4 seemed to look a lot cleaner than 2&3. Does this mean that I'm getting coolant into those cylinders?


    2nd Topic:

    Also I installed a oil catch can at 60,000K. every 5000 miles I dumped the stuff out (not so much) but I thought the catch can is going to help. I was wrong. I removed the Intake Manifold for clean up and I noticed the same amount of residue inside the cylinder head intake inlet. This time it was so much harder to clean; they were like gum (tar) and it took a long time to clean each inlet. I'm assuming that the catch can had something to do with how sticky the residue was this time compared to last time. I decided to remove the catch can and put back the original PCV valve pipe to the intake manifold.

    Now comes the questions,

    Can I just disconnect this hose completely so the PCV gases don't circulate back into the engine? Would I get any codes? I was thinking of plugging the inlet on the intake manifold and letting the PCV gas to just vent out.
     

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  11. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Maybe. Cylinder one in particular is the "usual suspect". How's the coolant level in the reservoir?

    Is it roughly 60K miles since the last intake manifold cleaning? I wouldn't count on an oil catch can to keep the intake pristine. First off, no oil catch can is perfect, they will catch some but not all. To illustrate, you can put two cans in series, see how much the second catches. Also, some oil seems to get spit back into the intake manifold by the intake ports.

    Also, not all oil catch cans are that effective. Does yours have internal baffling? Any reviews on it's efficacy?
     
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  12. Kasra

    Kasra Junior Member

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    Coolant level hasn't changed and I changed the coolant at 105K. Is there supposed to be a significant change in the level of the fluid?



    Yes it's roughly around 60K but I cleaned the throttle body (oil pool) a few times after some oil changes.

    As far as the catch can goes, I used the one that NutzAboutBolts used on their video but I filled it up with steel scrubbing pads. Can I just disconnect the hose from PCV to Intake Manifold completely to avoid this?

    Thanks
     
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  13. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Yes, if head gasket is failing and coolant is leaking into cylinder.

    First off, and especially in California, this is more'n likely very illegal.

    Too, I don't really understand the ramification of a disconnect, but think it would need to be done carefully. You'd want to plug the PCV inlet spigot on the intake manifold, to avoid a vacuum leak. And you do want to continue venting the crankcase, so maybe run an "open" oil catch can, the kind that has a filter on top, so you're venting to atmosphere but catching some of the gunk? Or just run a hose from the PCV valve down through the engine underpanel, so it can drip freely?
     
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  14. Kasra

    Kasra Junior Member

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    I'm actually trying to run an open catch can where the outlet to the Intake manifold is vented out (same as what I previously had set up, but just vent the catch can outlet tube into atmosphere. I live in Nevada now :D
     
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