How does coolant get in the Oil????

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by johnnychimpo, Jan 3, 2021.

  1. johnnychimpo

    johnnychimpo Member

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    So my 2010 is having cold start shakes and loosing coolant. I have cleaned the EGR system etc...
    I think its a blown head gasket as when I take the coolant cap off air pressure comes out and when I leave it off the car rarely shakes on startup. I found very faint white substance in the oil. This car has never burned oil so If this is coolant in the oil how is it getting there? is it going through the piston rings or is there a place in the head gasket that coolant and oil are close enough should there be a failure in the gasket they can mix? if so can some one provide an example pic so when I pull the head I can check? Also is there a procedure to check for bent rods? I would hate to do all this work only to find a bent rod down the road. side note I have only driven this car about a hundred mile since it started the cold start shake and I cleaned egr etc.. it has been parked since. Is this long enough time to bend a rod???
     

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  2. ChapmanF

    ChapmanF Senior Member

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    Re-reading your question, I don't have a definitive answer. The cylinder head does contain both oil passages (to lubricate the cams and operate the VVT) and coolant passages (to cool it), and both pass through the head gasket from the block, but I don't know how likely it is to pass coolant directly between those passages. It is certainly common for coolant to leak into a cylinder, and from there, find its way into the crankcase.
     
  3. Pluggo

    Pluggo Senior Member

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    One of my favorite graphics: 6 different ways a head gasket can fail. Notice: Blown to coolant port, water in oil.
    upload_2021-1-3_20-45-11.png
     
  4. johnnychimpo

    johnnychimpo Member

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    Thanks half, my answer so looking at this I dont suspect its the piston rings as car never consumed or burned oil. My last conern now is a bent rod. I need to figure out how to check for that.
     
  5. ChapmanF

    ChapmanF Senior Member

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    I don't think piston rings make perfect seals ... for one thing, they have end gaps. They're good enough for blocking most of the pressure and the oil while the engine's running, but I imagine if you leave coolant standing on top of a piston for a while, some's going to get in the crankcase. I could be wrong.
     
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  6. rjparker

    rjparker Senior Member

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    Agree
     
  7. johnnychimpo

    johnnychimpo Member

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    Im guessing/hope my issue is here. but such a small amount its hardly noticeable in the oil but definately enough for a cold start shakes. In any case anyone's thoughts on the bent rod and how long it would take for damage like that to occur? that is my biggest concern it is the difference between doing this over the weekend or getting a 2016 engine and having he mechanic do a swap.

    upload_2021-1-3_20-33-46.png
     
  8. johnnychimpo

    johnnychimpo Member

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    thanks for the reply very helpfull
     
  9. PTS

    PTS New Member

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    Some would say use a compression test but if you already have a blown head gasket differences in compression may not be definitive. A slightly bent rod may not immediately cause problems but the piston will press the cylinder unevenly leading to a larger failure later. So a mechanic will check the tdc heights very carefully after the head is removed. If necessary he can then change the affected piston and rod although on a Prius it requires pulling the engine.
     
  10. johnnychimpo

    johnnychimpo Member

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    found the answer and it is possible here.

    [​IMG]
     
  11. mr_guy_mann

    mr_guy_mann Member

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    Yes what you show is possible(and might account for coolant in the oil). however if you have engine "shakes" (misfire ) on cold startup then it is fairly certain that you have coolant leakage into the cylinder. It can hydrolock and damage the rod anytime that the amount of liquid in the cylinder is equal or greater volume than the combustion chamber size at Top Dead Center. Might happen next month, or next week, or who knows.

    Posted via the PriusChat mobile app.
     
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  12. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    The five stages of head gasket failure acceptance?

    (Google “the five stages of grief”.)
     
  13. ChapmanF

    ChapmanF Senior Member

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    I thought the OP was already at the acceptance stage in post #1 ("I think its a blown head gasket"), but just trying to pin down in what way it might have blown.
     
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  14. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Point taken. :)
     
  15. Peter123

    Peter123 Active Member

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    Something else to consider, If the engine gets too hot with coolant in the oil, the mixture can react and turn into a lacquer. Then when you let the engine cool down the lacquer will set and freeze the engine beyond any hope of repair. This historically has been a problem with mineral oil. I do not know what polyalphaolefin-based (synthetic) oils will do in a similar situation.
     
  16. rjparker

    rjparker Senior Member

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    Knock Knock Who's There?

    Stage 1
    Spark Plug and Coil Change
    Clean EGR
    Monitor Coolant
    Try Head Gasket Sealant


    Stage 2
    Order a Motor from Japan
    Arrange Killer Install Deal


    Stage 3
    Question Motor from Japan


    Stage 4
    Decide to Change the Head Gasket


    Stage 5
    Reconsider Motor if yours might have a Bent Rod
     
    #16 rjparker, Jan 5, 2021
    Last edited: Jan 5, 2021
  17. johnnychimpo

    johnnychimpo Member

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    Makes sense thx the leak is very tiny per coolant loss so thanks I feel better with explanation.
     
  18. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    I wonder could we include spark plug and coil change?

    Killer board game? :cool:
     
  19. rjparker

    rjparker Senior Member

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    Revised above
     
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  20. tvpierce

    tvpierce Senior Member

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    You can check for a bent rod by inserting a dowel (or other suitable straight stock) in a cylinder, rotating the crank to the top of the piston stroke, mark the dowel, then rotate the crank to the bottom of the stroke, and mark the dowel. Then use that for comparison across all 4 cylinders.
     
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