Testing valve seal after lapping valves on the cylinder head

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by nate358, May 30, 2022.

  1. nate358

    nate358 Junior Member

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    So I just got done lapping all the intake and exhaust valves and I was wondering if anyone knows of a test to test the seal before installing everything. I got all the valves back in and the springs on the valves. I put in the spark plugs turned the cylinder head upside down and filled each cylinder head with water. After 24 hours I came back and the water leaked through every valve. Do you think this means I didn't lap the valves correctly?

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    #1 nate358, May 30, 2022
  2. nate358

    nate358 Junior Member

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    #2 nate358, May 30, 2022
  3. ASRDogman

    ASRDogman Senior Member

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    If it leaks through, then they are not sealed. How did you do it?
    It's strange that everyone leaked. Which valved did they leak through.
    All exhaust? Intake? Combo?


     
    #3 ASRDogman, May 30, 2022
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    You'll get a better sense of it if you rest the head on its side and (alternately) fill the intake/exhaust ports, then watch for the leak on the combustion chamber face. This will help you work out which valves are leaking.
     
    #4 Leadfoot J. McCoalroller, May 31, 2022
  5. nate358

    nate358 Junior Member

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    I saw water laying in all the exhaust and intake ports after 24 hours. I used lapping compound and a lapping tool and hand spun the valves. Being my first time doing this... There is a good chance I didn't lap the valves correctly.

    When I was cleaning the cylinder head, I did put it on its side and the intake ports held water, but cylinder 1 and 3 on the exhaust side leaked.

    I'll try putting it on its side again and fill with water to see what happens before I take the springs off again. Sigh... Putting the retaining keepers on are a serious PITA.
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    #5 nate358, Jun 3, 2022
  6. ChapmanF

    ChapmanF Senior Member

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    Did you check the contact with Prussian blue while lapping?
     
    #6 ChapmanF, Jun 3, 2022
  7. ASRDogman

    ASRDogman Senior Member

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    Did you clean off the grinding compound after your lapped them? Use brake or carb cleaner
    and wipe the seat and valve and make sure you get it all cleaned off.
    It's off that ALL of them are leaking... This is why I ask...

    I forget the name of the stuff, but you can put it on the valve or seat and set the valve in,
    and rotate it. You should get a clean ring.

     
    #7 ASRDogman, Jun 3, 2022
  8. nate358

    nate358 Junior Member

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    I ended up ordering more fine paste to do the lapping with 400, 600, 1050 grit paste.

    FYI, don't use the water method... When I took it all back apart, water deposits and rust started to show and ruin all the work I did.

    I created a vacuum tester to see what kind of seal I could get. And after using the finer grits it was so much better. I couldn't get the seal I was looking for until I installed the valve springs, but with that vacuum tool I know the valves are no longer an issue.

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    #8 nate358, Jul 16, 2022
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    Full disclosure: I've never done head rebuild (or anything remotely close), but saw this video some time back, seemed to have good practices:

     
    #9 Mendel Leisk, Jul 16, 2022
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