2000 miles from home with rough startup knock

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Wyomingirl, Aug 22, 2025 at 3:04 PM.

  1. Wyomingirl

    Wyomingirl New Member

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    Hello Forum, this is my first post. I have a 2014V that I love for many reasons. I bought it from it's first owner (in AZ) with 66k on it, and in the last 6 years I've driven it up to 190,000 miles. It has been flawless. I've done oil changes, replaced the spark plugs and brake pads at 100,000 miles, and finally it needed a new 12V battery last year, but no other work. I live in WY, but drive long highway miles (to the east and west coasts at least every year). I am pretty car saavy, but I'm living in a summer apartment in Ithaca, NY, so nowhere near my tools or ramps in Wyoming.

    I just had the 190,000 oil change done (at a shop since I'm not at home--and they overfilled it, a little), and about 1 week later, it made the most terrible knocking for about 3-5 seconds right as the ICE kicked on. Then I heard nothing for about a week, and then it did this knocking a second time and the CEL came on. I took it to a shop. The code was for a 1st cylinder misfire, they changed the coil, and sent me on my way. I picked up my car afterhours, and the CEL was still on, and while it didn't misfire the 1st time I started it, the knocking happened on the ICE startup the subsequent time. I didn't like that shop --They also cracked my windshield (likely when they took the wiper assembly out), and the guy was slimy.

    By this time, I had found another local shop that has a better reputation. They did a pressure test, and found no loss. But the code was still for misfiring. They replaced all the coils and spark plugs (after 190k I don't begrudge fresh plugs). But this hasn't solved anything. They did a boroscope of the cylinders and don't see any sign of coolant leaking into. They did a 3 day higher pressure test and still didn't find any drop in pressure.

    They are starting to think there's a small crack in the head that opens up when cold and lets in a little coolant.
    I still wonder about the EGR being clogged up. Or a small crack in the Heat Exchanger on the exhaust pipe--how could they test for this?

    They are at a loss and waiting for me to 1)bring an engine to them to swap or 2) next test or thing to try.

    What should I have them test/do next? Any tips?

    I'm borrowing a car while mine is in the shop, and biking most places (sheesh--the hills around here), but I need to drive 2,000 miles back to WY in 6 weeks, and I want a car that will get me there.

    I plan to keep this car a few more years, until I can afford the next used Toyota hybrid that has this shape and space (Maybe CorollaCross? or Rav4).

    The cost of a HG job is more than to get a JDM and put it in, so that's why I was looking at an engine swap vs HG job. I'd love to keep my repairs under $7,000 but I'm already out $1,800 in coils and plugs and testing that has done nothing.
     
    #1 Wyomingirl, Aug 22, 2025 at 3:04 PM
  2. rjparker

    rjparker Tu Humilde Sirviente

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    Sorry to hear your in for $1800 worth of parts cannon with no results except a broken windshield. Unfortunately too many shops get fooled by a gen3 Prius.

    Pretty close but it's more likely the head gasket leaking while shutdown but with coolant pressure. Sometimes warped heads happen due to overheating but I doubt your there yet.

    The heat recirculation system is not causing a start up rattle. It's not a stuck open egr either; egrs will cause a stumble or stall at worse.

    I suspect the borescope test was not done properly under coolant pressure. The quality of the borescope is important as well.

    The following video was done by one of the best mechanics around and he is 75 minutes away from you.

    This was done on a Honda with a bigger leak but you will get the idea
    South Main Auto
    Excellent Borescope Footage at 6:50


    Assuming you have a leaking head gasket, you could limp along by relieving the coolant pressure by slightly loosening the passenger side reservoir cap.

    Assuming it is a head gasket (I would give it 95% likelihood) the question is how to proceed. A JDM would be the lowest cost solution but it would have to be shipped in from a bigger city and you would have to trust a local shop to change it. A head gasket job with a rebuilt head might be a good option if the engine does not burn oil and you do it fairly quick.

    I would consider taking it to South Main Auto if you can get in and let him diagnose and repair.

    South Main Auto LLC, 47 S Main St, Avoca, NY. Eric O
    IMG_9482.jpeg
     
    #2 rjparker, Aug 22, 2025 at 7:32 PM
    Last edited: Aug 22, 2025 at 7:40 PM
    BiomedO1 and Brian1954 like this.
  3. BiomedO1

    BiomedO1 Senior Member

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    IMHO; if it's in the early stages of HG failure; you may be able to limp it back home. You'll have to monitor your ECT to make sure you don't push it too hard on the way back. The BIG assumption is that the mechanic tested the car correctly and the leak closes up when the aluminum heats up.
    I'm not a big fan of JDM motors because your putting in another motor with a know defect. If the car is in good shape and your planning on keeping her - I'd probably look into a rebuilt motor with all the updates that negate the gen3 motors' deficiencies. In other words, JDM motors are a "crap-shoot", no telling how long they may or may not last.
    Whatever repairs you decide to do; you may want to preemptively replace that electronic ICE water pump. They tend to get lazy, especially if you don't change your coolant per OEM recommendations. Coolant goes acidic, quietly eating away at your engine internals - you've got a lot of plastic and electronics for the coolant to "chew on".

    Well; that's my rant for this thread - good luck....
     
    #3 BiomedO1, Aug 22, 2025 at 10:04 PM
    Last edited: Aug 22, 2025 at 10:52 PM
  4. rjparker

    rjparker Tu Humilde Sirviente

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    Not all JDMs have the same issues as a 2010 through early 2014 Prius. Used in Japan gen3 JDMs can be as recent as a 2021 as the Prius v/+ was still sold there until then. However there is no US vin plate to id the year so it's possible any 2010-2021 JDM could be in the crate you receive.

    Since you have a 2014 v, there is a good chance you have the revised pistons and rings. Verify by vin.

    Prius gen3 2014 Vin Production Change.jpeg
    Take your vin and determine which plant (3 or J) it was built in and then determine if your last six digits are higher than that plant's production change sequence number.

    An early head gasket job with existing revised pistons and rings will include an improved head gasket from Toyota or Felpro. A rebuilt head cleans things up in the valve train. Have the shop update the ecu software to 34751200.

    End result is you have a head gasket job with the same updates as a good gen3 rebuild. Assuming you have a first class shop do it.

    You could spend $225 more and include the latest intake manifold as described in the attached tsb. An improvement you don't get with most rebuilt engines.
     

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    #4 rjparker, Aug 22, 2025 at 11:01 PM
    Last edited: Aug 22, 2025 at 11:31 PM
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