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Broken rocker bridges

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Brenden, Jul 1, 2020.

  1. Brenden

    Brenden Registered User

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    D89E4D09-8D7E-4779-B4E8-6E392ED3D63F.jpeg 33F2A275-69AB-4270-A9FE-374FE61D56CE.jpeg C213194A-A9BF-419B-A7C2-FB05F8DB0159.jpeg 4D5A97AF-34F1-4DC4-83DA-1B7E4C4E590B.jpeg BEC5E2C7-299A-4A4D-B0D0-1EE36DDABA8B.jpeg I have a 1983 6.9 idi that won’t start anymore. The I’ve narrowed down the cause with all the troubleshooting I know.
    This all started when I was testing the 4x4 after I bought it. I drove through what I thought was a puddle and ended up being a 5 foot pond. Engine hydro locked. I dropped the clutch a few times on the dirt while it was getting winched onto the tow truck. Long story short I got the water out and it fired up, but seemed to only be running on 7 or maybe even 6 cylinders.

    The IP has been fully rebuilt and installed. I’ve verified and went through the trouble of being 100% positive the IP timing marks are lined up by removing the front cover.

    After this defeat, I decided it was time for head gaskets, but upon removing both valve covers, I noticed cylinder #2 had what I understand to be 7.3 rocker arms on it. And cylinders #1 and #8 have broken rocker bridges.
    When I turn the engine over with the starter, it sounds like I’m losing compression in a cylinder because the starter speeds up.

    Would these broken rocker bridges have something relatable to my issues?

    All I could think it would be would be: bent valve, head gaskets, piston rings and sleeves (since they were filled with dirty water), or maybe I’m dumb and it’s just old injectors.

    Any input is appreciated.
     
  2. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I won't say that the rockers is your issue, it may be (hopefully). BUT....there is a more likely situation (in my mind). I think that you have a bent rod or two. A liquid (water) doesn't compress as well as a gas (air/fuel mixture). Our engines only have a few thousandths of an inch of clearance between the top of the piston and the bottom of the cylinder head when it's at top dead center. Even if, by some miracle, the rods were fine after hydrolocking, you most likely bent one (or more) by dumping the clutch while the engine was in gear, being pulled. I know of a guy who bent all 8 rods while trying to drive across a flooded spot. We called him The Submarine Captain. Before you pull the heads off, you need to do a compression check. Use the 7.3 style rockers on the two cylinders that don't have them (just transfer them from another cylinder). I'm betting that one cylinder will have a big difference in compression due to the bent rod not being able to compress the air/fuel in that cylinder.
     
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  3. Brenden

    Brenden Registered User

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    By “all 8 rods” you’re referring to the connecting rods? Or half of the pushrods?
     
  4. riphip

    riphip Supporting Member Supporting Member

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    Connecting rods. Been there also
     
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  5. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Yep. I haven't been there though.
     
  6. Brenden

    Brenden Registered User

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    I'll give these things a try and post any progress. Thanks for the help.
     
  7. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I hate to be the bearer of bad news, but that's my first instinct. If worst comes to worst, maybe you could find a good running engine to swap in for a few hundred dollars.
     
  8. Brenden

    Brenden Registered User

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    Well I live for this kind of stuff so the only bad news would be how far I have to go with no progress to quench my thirst for fixing things.
     
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  9. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I was talking about the bad news on what I fear happened to your rods.
     
  10. rhythim

    rhythim Registered User

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    Yeah, I'm gonna go with at least 1 rod being shaped like a taco.

    Sent from my SM-G988U using Tapatalk
     
  11. riphip

    riphip Supporting Member Supporting Member

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    I would bet on more than 1 rod being bent but no tacos. Surprised it's not knocking like crazy, much less running. You have an '83 block (maybe) so check if there is a crack at the block heater freeze plug location over the starter. Better off with another engine. IMHO
     
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