Checking piston rings with diesel in cylinder

Discussion in 'Volvo Forum' started by bravoo67, May 12, 2012.

  1. bravoo67

    bravoo67 Light Load Member

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    How can I check piston rings on open volvo D12 engine without taking pistons out?? The head is off.

    I put around 1 inch of diesel in to each cylinder and after an hour it was almost gone..

    Is diesel appropriate and how long should it hold??
     
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  3. MNdriver

    MNdriver Road Train Member

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    it shouldn't hold any fluid in it for long.

    You have piston ring gaps and those should allow the fluid to by-pass rather easily.

    There will always be some cylinder leakage. the correct way to test it is with the heads on and then to put in compressed are and test for rate. That percentage should be close to the same for all cylinders.

    Just modify it for diesels. You pull the injector and put an adapter into the cylinder instead of a spark plug.
    http://www.supramania.com/forums/sh...to-Make-a-Leak-Down-Tester-amp-Perform-a-Test
     
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  4. bravoo67

    bravoo67 Light Load Member

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    I read about people putting WD40 or regular 10 40 engine oil..

    diesel seems to be the best just dont remember how long it should hold
     
  5. MNdriver

    MNdriver Road Train Member

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    you would put in some engine oil on a cylinder leak test as part of the test.

    you do both a "dry" and a "wet" test. When you compare those numbers, that tells you how well the engine is "sealed".


    No engine will ever be 100%. But wet, they should be over 90% or so. Dry around 75-80%. Maybe a little better.

    You are really looking for consistent readings as well across all the cylinders.

    If one is out of line with the others, that is likely the weak cylinder.
     
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  6. bravoo67

    bravoo67 Light Load Member

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    what is "dry" and "wet" test??

    Thank you!
     
  7. MNdriver

    MNdriver Road Train Member

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    check these out.
    http://www.freeasestudyguides.com/cylinder-leakage-test.html

    wet test will confirm if it's actually rings or if it's valves that are leaking.

    You test the engine "dry" first. This gives you base readings.

    Then you give each cylinder a tablespoon or so of oil for a "wet" test. They shouldn't really change much from the dry test.

    If the wet test gives much better results, then you have either a cracked ring or rings that are stuck and not sealing well.


    If the wet test is similar to the dry test, you need to look in the coolant for bubbles for leaking head gasket or cracked cylinders.

    If you hear air leak in the intake, it's bad intake valves.

    If you hear air leak in the exhaust, bad exhaust valves.
     
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  8. bravoo67

    bravoo67 Light Load Member

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    I get it now. Thank you for the info!

    but still need to check how long diesel/oil should stay in each cylinder
     
  9. Pablo-UA

    Pablo-UA Road Train Member

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    IMO. Bad Idea. To use laptop is easier.

    To check rings you have to pull injector out and with D12 brass sleeve goes bad after injector removed.
     
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  10. truckmechanic

    truckmechanic Medium Load Member

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    Use a camra with head on and injectors out and inspect the bore for Scoring or grooves if any are found and you can feel them with your fingernail then I would remove the pistons and get a better look if the heads off your already half way there I don't use the fluid method its not a fool proof way if its an egr motor with some miles it might loosen the carbon deposits on the ring lands and cause you big trouble I see major carbon deposits on egr motor not nearly as much on none egr depending on miles you might be able to run a hone through the liners and clean the carbon from pistons and our new rings and get some life out of her plus be a good time to roll in rod and mains
     
    Last edited: May 12, 2012
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  11. bravoo67

    bravoo67 Light Load Member

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    its egr engine with 620k miles and 4th cylinder got 74% on compression test with vcads.. all other cylinders were over 90%..

    i'm thinking of changing rings only on that 4th cylinder since I got the engine open


    Thank you for all the replies
     
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