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7.3 idi cavitation

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Va_Mike, Nov 9, 2019.

  1. Va_Mike

    Va_Mike Full Access Member

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    I'm heading to look at a engine today and just wanted to know what cylinders tend to suffer from cavitation more? Going to do a compression test on a few cylinders and want to make sure I check know problem ones.
     
  2. 79jasper

    79jasper Chickenhawk

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    Compression test wont show you anything about cavitation, unless it has gone through a cylinder wall. Even then, it could be such a small hole that you may not see it by the numbers.
    Just look for equal-ish numbers.

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  3. Garbage_Mechan

    Garbage_Mechan Garbage Mechanic

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    More telling on cavitation that has pinholed the cyl wall is signs of moisture and white/ grey slime under the valve covers, oil filler cap or in the CDR valve. I’ve seen them run fine with a pinhole except the above symptoms till one day the piston ends up parked below the pinhole for a few hours. Hydrolocked.
     
  4. chris142

    chris142 Full Access Member

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    I think it's pretty rare really. In the past I have seen complete disaster cooling systems,completely clogged with rust and no holes in the liners.
     
  5. Garbage_Mechan

    Garbage_Mechan Garbage Mechanic

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    I’ve seen 2 IDI’s personally. One was a 1990 in 1994 with 100,000 miles. That one hurt my young pocketbook.
    Had one DT466 do it in 3000 hours. ( Fresh rebuild, mechanic forgot the coolant additive.) Small and Big Cam Cummins always had pits in the liners when pulled. Sometimes through.
    I’d think there may have been blocks that were more prone to it that were weeded out of the pool by now.
     
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  6. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Well said. I also believe that most the cavitation incident blocks have shown up by now, you almost never see it happen any more.
     
  7. chris142

    chris142 Full Access Member

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    Ya those 855's would get the block worm if the coolant and addatives were not kept up. My 1962 Nt280b was still going when I sold it in 2012.
     
  8. Garbage_Mechan

    Garbage_Mechan Garbage Mechanic

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    What was the NT in? I’m not familiar with that designation. Had an NT743 that had some odd heads on it in a Galion Grader.
     
  9. ifrythings

    ifrythings Full Access Member

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    Everyone says cavitation is so rare till it happens to you. #8 cylinder right in the center.
    C97EC544-26FA-4A42-B944-1C4FBEFFD0CA.jpeg
     
  10. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Looks like the piston skirts were eating into that side of the cylinder wall which doesn’t help it, when was that?
     
  11. ifrythings

    ifrythings Full Access Member

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    I’m guessing those holes were there before I rebuilt the engine and had 20 thou taken off. Didn’t realize it at the time but when I broke down the engine and a gallon of clear water came out before oil started draining would of been a good clue on the health of this engine. I was told by people that if it made it past 100k it would be fine, this had just over 400k so I didn’t even look for problems like this, didn’t know much out diesels or idis at that time.

    Machine shop was very helpful with all the problems I had with this engine and they sleeved #7 and #8 for free. If I were to do it again I would definitely consider sleeping every hole or at minimum #7 and #8 hole.
     
  12. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Yeah with 400k I would sleeve the whole thing too. I like finding engines with around 150k for builds, not much wear but enough to ring out the bad blocks.
     
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  13. Blackascoal

    Blackascoal Registered User

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    Is it safe to say if you make it to 150k without cavitation you’re probably not going to encounter it? I’m right about there with my 94.


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  14. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    I wouldn’t worry about it. We’re much more likely to get hit by a drunk driver than to experience cavitation issues. I’ve had more casting flaws lead to premature rod failures in na blocks than I’ve seen cavitation in a virgin bore blocks, and even that’s a huge minority.
     
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  15. IDIoit

    IDIoit MachinistFabricator Supporting Member

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    the only way to "check" cavitation is by sonic testing.

    I have recently been on the wrench with 3 different blocks.
    I was looking to put a solid runner together for a project I am working on.
    I bought 3 different blocks for 1-200 a piece.
    out of 6 heads, 3 were cracked."
    one block, which was a turbo block, had a bent rod.
    the other 2 short blocks were pretty nice after you cleaned the sludge out of them.
    all bearings were within spec.
    I had a freshly set of machined heads on the shelf.
    made 1 solid engine
    all new gaskets, injectors and a pump is on its way.
    the other good short block, is getting a set of the uncracked heads.
    lapped the valves, and checked the guides.
    checked the valve recession...
    just waiting on studs!

    moral of the story.
    treat every block you buy, as a "core"

    73342362_144538066832606_2094543339943624704_n.jpg

    73539221_146150170004729_161365404529197056_n.jpg

    74268507_146150480004698_3094142642456363008_n.jpg
     
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