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Loud knocking coming from rear of engine?

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    #1

    Loud knocking coming from rear of engine?

    There is a loud knocking sound coming from the rear of the engine. its not the valves, or spark plugs.
    sounds kind of like a desiel engine.

    its only on throttle, sound goes away when engine is slowing down.

    aslo my starter is going out, could this be contributing to this sound

    any ideas?
    m106 1990 e30
    e36 daily
    e32 cruiser
    Tags: None
    #2
    LOUD knocking? Is there a thumping that you can feel also? It could be the guibo or the driveshaft center support.
    '88 528e /// '88 M5 /// '89 951 /// '98 E430 /// '02 M5

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      #3
      no, it also does it in neutral so it would have nothing to do with the tranny/driveshaft
      m106 1990 e30
      e36 daily
      e32 cruiser

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        #4
        Starter solenoid allowing the gear to randomly hit the flywheel?
        I Timothy 2:1-2

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          #5
          It could be the start of the crank starting to destroy itself.

          Does it do it when the motor is idle or just when the car is in motion??
          Your signature picture has been removed since it contained the Photobucket "upgrade your account" image.

          "I cannot undertake to lay my finger on that article of the Constitution which granted a right to Congress of expending, on objects of benevolence, the money of their constituents. Charity is no part of the legislative duty of the [federal] government." ~ James Madison

          ‎"If you've got a business, you didn't build that. Somebody else made that happen" Barack Obama

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            #6
            Hi, a friend of mine had a similar sound in his luv, when you pressed the clutch it went away, we all blamed it on the clutch, but when we dissasembled everything it was crankshaft end play.
            Use a long rod, press it to the engine and press your ear to the other end, place the rod in different areas of the engine/tranny, that will tell you exactly where the noise is coming from (and make it clearer for you to identify the pitch and area).
            I said a long rod because an automotive stethoscope is not easy to find.

            good luck.

            BTW if it's on top of the engine could be a piston pin, if it's on the bottom a rod or crankshaft bearing.

            Comment

              #7
              Originally posted by joshh View Post
              It could be the start of the crank starting to destroy itself.

              Does it do it when the motor is idle or just when the car is in motion??
              the sound starts when the r3v's are at approx 2500-3000 (my tach doesnt work, so im guessing)


              Originally posted by markseven View Post
              Starter solenoid allowing the gear to randomly hit the flywheel?
              i hope so, i have another starter that im going to put in today.
              m106 1990 e30
              e36 daily
              e32 cruiser

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                #8
                took it to my mechanic today. cylinder 3 has a broken rod bearing, possible damage to crank and rod.
                both motor mounts are broken.
                m106 1990 e30
                e36 daily
                e32 cruiser

                Comment

                  #9
                  Originally posted by Rennsport View Post
                  took it to my mechanic today. cylinder 3 has a broken rod bearing, possible damage to crank and rod.
                  both motor mounts are broken.
                  That sucks. M50?:D
                  Originally posted by cabriodster87
                  "Honey? What color is this wire? Is it the same as that one? Are you sure? I don't believe it. OK, it works. Thank you sweetie."
                  Originally posted by Kershaw
                  i've got a boner and a desire to speed.

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                    #10
                    Good luck with the fix.
                    Your signature picture has been removed since it contained the Photobucket "upgrade your account" image.

                    "I cannot undertake to lay my finger on that article of the Constitution which granted a right to Congress of expending, on objects of benevolence, the money of their constituents. Charity is no part of the legislative duty of the [federal] government." ~ James Madison

                    ‎"If you've got a business, you didn't build that. Somebody else made that happen" Barack Obama

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                      #11
                      thx, this will be my first time tearing an engine down to this extent, but it will give me good experience for the future. ill take pictures!

                      unfortunatly my other engine (2.7 building for turbo) isnt anywhere close to being completed, otherwise now would be the perfect time to drop it in.
                      m106 1990 e30
                      e36 daily
                      e32 cruiser

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