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GM techs and Vortec truck owners, Rod Bearing knock?

Discussion in 'The Garage' started by sled_dog, Feb 22, 2006.

  1. sled_dog

    sled_dog 1 ton status

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    Anyone experienced a cold rod bearing knock from their Vortec engine? I was bored at work today(very very slow) and started looking up all the service info on my daily driver since it has a few issues. One of them is when it is really cold it has a rod knock at low rpms. There is a TSB for that exact thing, a cold, low rpm rod knock. Recommends new rod bearings. Also stated that some of the Vortec engines have a problem with crank bearings. Anyone tell me how to tell if my rig is affected by the crank issue other than pulling the oil pan? And anyone dealt with the rod knock thing? I was kind of figuring if the engine has to come out I might as well slap together another one so all I have to do is pull the intake and wiring assembly and throw in a fresh, maybe more powerful engine.
     
  2. dogdaysunrise

    dogdaysunrise 1/2 ton status

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    My motor does that, it lasts for about 10 seconds then goes away once the idle comes up.
     
  3. ryan22re

    ryan22re 1/2 ton status

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    ive seen plenty of vortecs both 4.3 and 5.7 go out after an intake manifold change. always the rod bearings though. seems that abrasive discs and cleaning the cast iron dont mix.

    havent seen one go from just wearing out though. fwiw over the last 4 years at gm dealer.
     
  4. DEMON44

    DEMON44 Low-Tech Redneck

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    Research a term called "piston slap"


    You'll find that is what you have for the 10 or so seconds when you first fire up.
     
  5. ryan22re

    ryan22re 1/2 ton status

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    piston slap is for the gen III/IV engines.

    vortec engines like sleds are the old 350
     
  6. sled_dog

    sled_dog 1 ton status

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    its not piston slap. Well it can sort of be piston slap. The TSB clearly states it is a rod bearing issue. Like Ryan said, Piston slap is a Gen III/IV engine issue not Gen I Vortec.
     
  7. 85mudblazin

    85mudblazin 1/2 ton status

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    My Vortec 6.0L in my 01 Chevy 2500 does it. It only does it when its cold out and lasts until the engine warms up. The 6.0's are notorious for this and ive never heard of it causing any damage. I just liek to think that I have a diesel in the morning:D
     
  8. DEMON44

    DEMON44 Low-Tech Redneck

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    Ah, when you said vortec. thats the first thing that popped into the knoggin. Didn't know you had an older one.
     
  9. dogdaysunrise

    dogdaysunrise 1/2 ton status

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    mine is an older block as well

    actually its not a vortec...
     
  10. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    My 98 does that sometimes.... I run the piss out of it and nothing has happend yet... Wonder if theres anything that could be done, mine only has 63k miles on it... I had never really read the TSBs. Fill me in further Allan
     
  11. sled_dog

    sled_dog 1 ton status

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    I'll try and print the TSBs if I have free time today. Mine has a little over 100K on the clock and just recently started doing this.
     
  12. neverendingproject

    neverendingproject 1/2 ton status

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    At my uncles JY, nearly alll of the vortecs we saw ha either a spun rod bearing or cracked head, and usually both.
     
  13. Hermy13

    Hermy13 Registered Member

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    After changing my great leaky intake gaskets 1000 miles down the road the crank welded up on the bearing. 150k on it
     
  14. beater_k20

    beater_k20 Banned

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    i havent owned an 88-96 truck that didnt do it. never had any problems out of them either.
     
  15. sled_dog

    sled_dog 1 ton status

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    was that an internal coolant leak? That would make sense, antifreeze destroys bearings. The intake leak I had was an external one.
     
  16. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    I have a 79 350 with 125000 on the short block, that has been doing it for about 50000 miles now, a cold start up will knock for about 5-7 times then quiets down, and sounds normal.
     
  17. owen

    owen 1/2 ton status

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    Is this the engine that requires the "check-valve oil filter"? I know most of us throw the same old filter on as we do our other Chevys, and that might be a problem. Does this ring a bell with anyone?
     
  18. fatbob

    fatbob 1/2 ton status

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    I was talking to the owner of an engine shop about putting a serpentine belt setup on my old 400 and he advised against it.
    He has a newer chevy p/u an went over to it, started it up, and pointed out the slight knock on startup.
    His theory was the extra grip the serpentine belt provided, caused the crank to move untill it got oil pressure at the bearing. He said the engines are still quite tough, they all do it, and GM wont do anything for it. But he would not recommend putting the serp. setup on my motor.
    Now that is his viewpoint, but he has much more knowledge than me in this area, so I'm thinking of taking his advise and sticking with V-belts
     
  19. sweetk30

    sweetk30 professional hooker Premium Member

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    same hear buddy.:rolleyes:
     
  20. sweetk30

    sweetk30 professional hooker Premium Member

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    good point but the check valve only is needed for the filters that mount up side down. this is to keep oil in it when off. are filters mount up on the old motors. and the 88-up 4x4s run a smaller one that mounts sidways .
     

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