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2012 Prius C Engine noise

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by Species5618w, Apr 28, 2023.

  1. Species5618w

    Species5618w Member

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    I got a 2012 Prius C at 180k km. Every morning, the engine makes a weird knocking noise about 1 minute into the startup cycle and then it goes away. When driving, there's a tapping or clicking side as I accelerate. Any ideas what it could be? Thx.

    p.s. Spark plugs were recently replaced.


     
  2. bisco

    bisco cookie crumbler

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    are you losing any coolant?
     
  3. Sonic_TH

    Sonic_TH Member

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    Report coolant level.
     
  4. Species5618w

    Species5618w Member

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    Good question. Coolant level is between Full and Low, which is kind of weird since I got my coolant replaced about a year ago. You'd think dealer would have filled it to full. I never checked though. I should keep an eye on it and report back if it goes down further.

    Please don't be head gasket.
     
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  5. bisco

    bisco cookie crumbler

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    another possibility is the egr valve
     
  6. Sonic_TH

    Sonic_TH Member

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    I don't think it is the head gasket, what i think it could be even though i have not hear of it happening in the Prius C, is the heat exchanger it has neart he catalytic converter, to circulate engine coolant there to warm the engine faster, i think that could leak and let the coolant go into the exhaust.
     
  7. Species5618w

    Species5618w Member

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    Someone on reddit commented that it might be the VVT actuator. Apparently it's a common problem on early Prius Cs until they fixed the part. Chatted with the dealer, they recommended a fuel injector cleanup. Sigh...
     
  8. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Why would the VVT actuator be doing anything at all when the engine is at low and steady RPM?

    Also the ECU has at least a few things watching out, ready to spring check-engine warnings for over or under-advanced cam timing.

    Your car doesn't sound exactly like ours, but it didn't sound concerning to me in that clip.
     
  9. Species5618w

    Species5618w Member

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    The engine sound is fine at the beginning, however, at the 1 minute mark, the RPM revs up as part of the normal warm up cycle, that's when the engine starts to knock. Once the RPM comes down, the knocking stops. When driving while cold, the engine makes similar sound when stepping on the gas. Gets less noticeable once it warms up, although still auditable. The guy said that a lot of hybrid yaris started to have timing chain issues at 150k km, although he thinks it's the actuator in this case. He suggested to get the timing chain replaced anyway while in there.

    Is there anyway I can see the check-engine warnings in the dash or do I need to buy a code reader for it? The engine light never turned on.
     
  10. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I heard the change, I would've characterized it as valve tap. I've owned a number of cars that did similar during warmup, and it never mattered to those cars. This is largely why I say I didn't hear anything concerning.

    You should see the check engine light when you turn on the ignition without proceeding to READY mode- that's a lamp test so you can be sure the indicator actually works.

    You might to be able to pull codes from the car by shorting the right pins on the OBD interface. Blink code instructions. I've never tried it on a c model, so I don't know if it works the same as with the bigbody Prius.
     
  11. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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  12. Species5618w

    Species5618w Member

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    Ah, I see. Thank you. I will keep an eye on the coolant level and see whether it drops any further. They also seem to have overfilled my engine oil last time. I will need to do another oil change soon and I will keep an eye on that as well.
     
  13. Species5618w

    Species5618w Member

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    Ah, I see. Thank you. I will keep an eye on the coolant level and see whether it drops any further. They also seem to have overfilled my engine oil last time. I will need to do another oil change soon and I will keep an eye on that as well.
     
  14. Gavin Sun

    Gavin Sun Junior Member

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    Maybe a damaged or worn-out engine mount can cause vibrations that may be mistaken for knocking or tapping sounds.
     
  15. Species5618w

    Species5618w Member

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    Thx. Doesn't feel like it as the engine was not excessively shaking. But definitely a possibility.
     
  16. ChapmanF

    ChapmanF Senior Member

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    My guess is that some of the ECUs in a c will play along, but it's never all of them. Looking for engine codes, I don't think the ECM has ever been one of the ECUs that will blink codes, in any Prius.

    You can always go short those pins one day just to see which lights on the dash blink. If the ECU has no codes for you, its light will just give a fast steady blink. So you can see, any time, which ECUs have that ability.

    For codes from the ECM, the good news is, pretty much any old scan tool will show those.
     
  17. Tyler S

    Tyler S Junior Member

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    I have the exact same issue/sound with mine at 255k km. Mine started doing this around 220k km but it didn't necessarily get worse at cold start and largely disappears once the engine is warm (or approximately 10 minutes into driving).

    Over the past couple of days I have noticed a bit of a misfire when the vehicle goes through its warm up cycle when parked. Have you noticed this on yours as well? And did you end up getting this resolved?
     
  18. Leon Kernan

    Leon Kernan Junior Member

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    Mine has been doing that for a while now at around 240,000km. There were no codes and no misfire counts but it sounded like one.
    I finally replaced the PCV this morning and it seems to have gone a long way to solving the problem.

    As you can see, the old one was a mess.
    [​IMG]
     
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