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Piston Ring problem / low oil ??

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by PriusNeckBeard, Nov 14, 2018.

  1. PriusNeckBeard

    PriusNeckBeard Active Member

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    This is a long post.
    Sorry about that.

    Essential Facts and Actual questions are in bold.
    Feel free to read only those.


    A while ago, I changed oil at 10,000 miles. Per Toyota's %$&$(&*% instructions.
    Oil was like 2.25 quarts low. Maybe 2.5. Thanks, Toyota.

    It's been losing oil.

    I seemed to read on the 'nets that this can damage piston rings.
    Which has an accompanying loss in acceleration.


    In early September, by my measurements, it had lost perhaps 0.6-0.7 quarts of oil and thereby seemed on track to lose 1 quart by 1,100-1,300 miles. Which is Toyota's standard for 'needs repair'. That is, IF the space between the dots on the dipstick is linearly related to oil loss. i.e. it was about 1/3 of the way down and the dipstick difference between upper and lower dots is 1.6 quarts.

    So, I took it to the dealership, which did an oil consumption test.
    They said they topped it off perfectly full, and then I was to drive 1,100 - 1,300 miles.
    I brought it in after 1,200 miles.
    Per their protocol, they added exactly 1 quart of oil.
    The oil showed ABOVE max on the dipstick.
    Therefore, they concluded that I had lost less than 1 quart of oil, and didn't need repair.
    But they don't estimate how much oil was lost... could be .9 quarts, could be .5....who knows.
    They only recommend repair if loses more than one quart in 1,100 - 1,300 miles.

    Right now, I'm doing a personal follow-up test of my own, just to be sure. Today, it's been 954 miles since the dealer test, and I'm checking the oil (did that today), and will again at 1,300 miles. I want to see the exact severity of the problem. If it's very close to 1 quart down at 1,300 miles, then I may have them re-do the oil consumption test.

    I'm not satisfied.

    1. Mostly because I sense a loss in acceleration when the oil is down, and I guess I'm .25 quarts down. Perhaps not noticeable to others, but annoying to me.

    When the oil is perfectly topped off, I'm not sure I notice a loss in acceleration.
    (though I suspect that if it were suddenly undamaged like before, I suspect I would notice an improvement in instant acceleration response). (it's kinda like windshield wipers...may seem fine, but switch to brand new and you'll see a difference).

    Before this problem, in PWR mode, I thought acceleration was totally fine, and GREAT for passing. Never having had a sports car, and coming from a big SUV, I felt it was excellent and bumped me up when I was going 40 MPH on larger roads or 60+ mph on the freeway and needed to bump up by 4-10 MPH to pass someone or make a move.

    Now, only when perfectly topped off, I would say it feels totally fine, and I'm satisfied. to be fair, it's possible it does not have magnificent instant umph like before, but it does so well that I'm not sure I notice.

    Whereas, today, 954 miles since the dealer test/perfect top off, I'm .25 of a quart down (if the dipstick is linear...), and I notice the loss in acceleration, though it's not at it's worst.

    2. I'm truly surprised at how little oil has been lost in the past 954 miles. Is cold weather slowing down my oil loss??? At this point, I thought I'd be down .6 or .7....but I'm only down .25 (I think).

    3. Does piston ring damage cause a loss in gas mileage? Anybody know?
    I've noticed I'm getting like 38 MPG and I'm filling my tank more often since 'the incident'.
    Previously I was often at 42 or 43.
    I make a lot of short trips. (Most are 10-mile trips, the rest are 1-3 miles long).

    This was before the temperature dropped. I'm in the midwest; it only recently dropped to the 30's 40's.

    4. I do plan on figuring out the cost of the problem of course. (cost in lost gas mileage, added oil over time).

    5. Does anyone know if this problem (piston ring damage?) will get worse over time?

    Also...I'm under an extended warranty.
    I could do another oil consumption test at 99,000 miles.


    Thanks
     
    #1 PriusNeckBeard, Nov 14, 2018
    Last edited: Nov 14, 2018
  2. padroo

    padroo Senior Member

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    As long as the oil level is high enough to not starve the system of oil there should be no change in the engine operation. It is a force fed system not a splash lubrication system.

    I would do at least a compression test or better yet a leak down test and that should give you a good indication of the engines ability to make power. This takes care of the mechanical side of the engine and does not include the electrical and electronic part of troubleshooting but is a good start.

    I wonder what your HV battery health is like?
     
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    Have you got these TSB's? (I'll attach)

    The oil consumption test is word-for-word per the first TSB. For what it's worth oil consumption of 1 quart in 1100 to 1300 miles (the criteria in the TSB) is less extreme than the BS in the Owner's manual (something like a quart every 600 miles?).

    Hey, if there's a repeat of that test: drive repeatedly up the steepest hill you can find, daily. And go back to the dealership as close to the 1300 mile limit as possible.

    In model year 2014 the pistons were revised, and in model year 2015 the piston rings also were revised. In a nutshell, he repair TSB entails swapping out pistons and rings for 2015 versions, the inference being that these are better, don't lead to oil burning as much.

    upload_2018-11-14_9-52-16.png

    Here's breakdown of the parts costs, using part numbers in the tsb, assuming just the engine is pulled, the transaxle is left in the car:

    upload_2018-11-14_10-6-31.png

    The gasket kit I think includes a new head gasket? Maybe you could cheap out, avoid replacing the pistons, just do the rings? Just thoughts.
     

    Attached Files:

    #3 Mendel Leisk, Nov 14, 2018
    Last edited: Nov 14, 2018
  4. bisco

    bisco cookie crumbler

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    how many miles on her?

    what does the extended warranty say about excess oil consumption?

    do you check your oil level regularly between changes?
     
  5. Mendel Leisk

    Mendel Leisk Senior Member

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  6. mjoo

    mjoo Senior Member

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    Yes if it results in lower compression. Burning oil results in more soot production in the exhaust and knocking. This leads to accelerated EGR clogging. A clogged EGR circuit also reduces fuel economy.

    Yes but no one knows for sure how much time yours has.

    Fuel system cleaners were found to help with oil consumption.

    A select few have testified that piston soaks can free the rings. This works if there's no physical damage to the engine. Having driven a Saturn S-series back in college - I believe in piston soaks.

    Also clean your PCV and EGR systems and install an OCC so that you can save the head gasket.

    Pixel XL ?
     
    #6 mjoo, Nov 14, 2018
    Last edited: Nov 14, 2018
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  7. Grit

    Grit Senior Member

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    Paid a premium price for it, put it to use (y)
     
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  8. PriusNeckBeard

    PriusNeckBeard Active Member

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    These responses were awesome.
    I'm going through them one at a time.

    re: "I would do at least a compression test or better yet a leak down test and that should give you a good indication of the engines ability to make power."

    They did the oil consumption test for free.
    In case they want to charge for compression or leak down test,
    What would be an outcome of these test, so I'll know if it's worth paying for?

    i.e....considering that the engine IS making enough power to drive just fine, do you think it possible that still, the engine power could be low enough to instigate a warranty-covered fix ? (is that where we could be going with this ?)
     
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    Have you seen this:



    Eric the Car Guy's leak-down test. He has problems with his (new) tester, I believe ends up using a compression tester with the schraeder valve removed. I believe what this does (I need to watch the video again) is pressurize a cylinder, that's at top dead center on the compression stroke. You might actually be able to DIY this, with just a modded compression tester. I'm not sure how strong a source of compressed air you need. I (for example) have a might-vac kicking around, not sure if that'd be sufficient. You basically pressurize the cylinder, and then go around, looking for air leaks: where they are pinpoints potential problems.

    About 19:30 in, he gives up on his tester and goes with modded compression tester.

    Step one doing this on a prius would be to remove the wipers and cowl, all the stuff required for a spark plug change. I think you'd be looking at a couple of hours labour, all told?
     
  10. alanwagen

    alanwagen Member

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    One guy on here used 6 tanks of gas with Techron and it de-carboned his rings and reduced his oil consumption. It's a known problem with the carbon. Also use ONLY Tier 1 gas .
     
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