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1999 Tacoma 2.4L loud knocking sound only when warmed up 222K miles

Discussion in '1st Gen. Tacomas (1995-2004)' started by gdaddy, Apr 2, 2020.

  1. Apr 2, 2020 at 11:24 AM
    #1
    gdaddy

    gdaddy [OP] New Member

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    Took it to a good, honest mechanic. First listened to front of engine with stethoscope. He believed it was coming from bottom of engine. He disabled #1 injector, sound went away. Reconnected, came back. Dropped oil pan to replace rod bearings. Could see no issue. Checked thrust bearings, could find no issue. Replaced all rod bearings. After engine warmed up, knocking returned. I told him I thought it could be timing chain or guides. He checked front of engine and said he could feel vibration coming from oil pump. He disassembled the oil pump and could find no problem. He replaced oil pump and just to take no chances replaced the timing chain assembly (everything). He even replaced the harmonic balancer. The sound was still there! He told me he does not have anymore ideas at this time. $3800 in parts and labor, and he didn't charge me because he couldn't find the problem!

    Any ideas?
     
  2. Apr 2, 2020 at 11:28 AM
    #2
    Black DOG Lila

    Black DOG Lila Well-Known Member

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    Stock. EZ pass.Dump pass.Inspection sticker.Convict printed lic.plates.FG cap.
    Welcome aboard new member
     
  3. Apr 2, 2020 at 12:12 PM
    #3
    Old n' slow

    Old n' slow Well-Known Member

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    This seems too obvious to me so maybe I’m missing something. After disconnecting injector #1 and the knock going away, I would have dug further into #1 cylinder. If the rod bearing didn’t do it I’d be checking wrist pin and piston next. Of course not hearing the sound it made makes it difficult to second guess.
     
    Black DOG Lila likes this.
  4. Apr 2, 2020 at 12:43 PM
    #4
    gdaddy

    gdaddy [OP] New Member

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    I asked him about the wrist pin being loose. He said they tighen up as they get hotter.
     
  5. Apr 2, 2020 at 12:54 PM
    #5
    Old n' slow

    Old n' slow Well-Known Member

    Joined:
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    Oak Island, N.C.
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    2000 Tacoma 2.4 5 speed flare side
    True.......pistons being aluminum warm up and expand so piston slap and wrist pin noise usually get better.

    That’s all I had.......so I’ll get out of the way now and follow this.
     

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