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Diagnosing engine noise

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  • #487951
    WilsonWilson
    Participant

      I have a 2002 Toyota 4Runner with over 100K. Now, at random, whenever the car starts, a loud squeal is heard from the initial rev to fast idle which last about 1-2 seconds. Since it’s not constant, I can’t provide audio evidence. I like to know how to locate and eliminate the source?

    Viewing 8 replies - 1 through 8 (of 8 total)
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    • #488136
      Nick WarnerNick Warner
      Participant

        Have someone start the engine while you look under the hood at the a/c compressor. When this noise is present, is the compressor engaged? You would be seeing the center of it turning with the outer ring that the belt rides on.

        #488189
        college mancollege man
        Moderator

          Have you ever changed the belt?

          #494972
          WilsonWilson
          Participant

            I’ve check the belts and they are good. The A/C clutch is not the problem because the squeak is there when the A/C is turn off. Now the squeak are getting more frequent and louder.

            #495818
            Nick WarnerNick Warner
            Participant

              It actually makes it easier to diagnose when it gets more consistent. Intermittent issues are terrible even for the pros. Get a spray bottle of water and spray down the belt. Start the motor and spray a bit more. If there is no noise when there usually is you have a bad belt, and I would change the belt, tensioner and idler pulleys as a set with Gates units so you don’t have failures later. You said you checked the belts and they were good. Well not all bad belts look like they are about to fall off. Try the water test and let us know what you come up with.

              #496110
              montelamontela
              Participant

                if the sound is frequently now try t remove the belt of alternator while the vehicle is running and watch the sound if it disappeared so the alternator belt is faulty if same sound still so remove other belts and check sound

                #496129
                college mancollege man
                Moderator
                  #500769
                  Paul RPaul R
                  Participant

                    When you start your engine and get a belt sequel that last a few seconds and goes away. Look to the alternator belt. An alternator will put a heavy drag on the belt right after start up to recharge from the power used by the starter. If you run down the battery a bit say 5 minutes of headlights before you start the engine. The noise should last a bit longer maybe sound louder. Might help to diagnose.

                    #501183
                    WilsonWilson
                    Participant

                      Say if it is the alternator belt, should it be changed?

                    Viewing 8 replies - 1 through 8 (of 8 total)
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