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Is this rattle early head gasket failure?

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by lrisius, Oct 18, 2023.

  1. lrisius

    lrisius Member

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    Location:
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    Vehicle:
    2015 Prius v wagon
    Model:
    Three
    Background: 2015 Prius v, 116k miles, egr cleaned at about 100k, oil catch can installed at about 60k. Original owner. Car has never overheated. Local morning temps in the low to mid 40s.

    In the last 2-3 weeks, this car has had gentle rattle upon a cold start three times that generally lasts a few seconds and then runs normally. A gentle rattle is the best description I can come up with- it isn't the violent "it sounds like a rod being thrown" that some of the videos here show. The first time I thought it sounded like a heat shield but I'm not sure that is likely with the v. It happens maybe every 4th or 5th cold start. No dash lights come on and no codes when I pulled them. Coolant level doesn't appear to be dropping, but if this is head gasket, we are probably very early. No milkiness in oil but that doesn't seem to be a common symptom either. During the most recent incident, it seemed like it was ok for a few seconds, then rattled for a few seconds and then returned to normal. This seemed to fit a thread I read about condensation in the intake manifold getting pulled in.

    So, does this sound like early stages of head gasket trouble or are there other likely explanations? What is the best way to confirm head gasket- would a bore-scope show something this intermittent?
     
    #1 lrisius, Oct 18, 2023
  2. bisco

    bisco cookie crumbler

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    It’s certainly a possibility. With everything clean, the only other thing I can think of is incomplete combustion due to short cycling the previous start
     
    #2 bisco, Oct 18, 2023
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  3. lrisius

    lrisius Member

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    Three
    That is an interesting thought. I think the first time it happened, it had been run earlier in the morning and then re-started after sitting for a few hours. The other two times it had been sitting overnight.
     
    #3 lrisius, Oct 18, 2023
    Last edited: Oct 18, 2023
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  4. rjparker

    rjparker Tu Humilde Sirviente

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    Vehicle:
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    Lots of egr and intake theories were circulating 5-7 years ago on Priuschat about cold start rattles. Until a huge number of hg fails began happening across the nation. All caused by misfires with a very few traced to plugs or coils. But they don’t clear up fast and are not random.

    But a 2015 has better pistons and rings which will reduce the gummy hydrocarbons in the intake, valves and egr cooler.

    Time will tell. Often it’s months before the rattling occurs on acceleration from stop signs and months again before white smoke and a rapid decrease in coolant makes it obvious to the average mechanic.

    A quality two view borescope in the hands of an experienced observer often notes a cleaner piston from steam cleaning and sometimes can catch coolant seeping from a warm and pressurized coolant system.


    Car Care Nut HG Borescope at 10:57


    This is another engine but the process is the same. He starts by looking at a spark plug.

    He mentions egr as a possibility. Only if stuck open allowing exhaust flow at idle since the egr closes at low rpm or startup. Stuck open egrs are not typical on a Prius that tend to clog egrs. But an egr that is stuck open will stay open and not quickly clear. In mid 2014 Toyota revised pistons and rings which helps reduce hg frequency.
     
    #4 rjparker, Oct 18, 2023
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