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High pitch howel from engine. Not belts. Need advice.

Discussion in '3rd Gen 4Runners (1996-2002)' started by Kotletachka, Jun 10, 2020.

  1. Jun 10, 2020 at 6:33 PM
    #1
    Kotletachka

    Kotletachka [OP] New Member

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  2. Jun 11, 2020 at 9:02 AM
    #2
    negusm

    negusm New Member

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    Power Steering fluid topped up? (youtube is blocked where I'm at but if it's not belts it's often the steering pump.).
     
  3. Jun 11, 2020 at 10:23 AM
    #3
    4x Old Guy

    4x Old Guy New Member

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    Sounds like a vacuum leak.

    At idle, manifold vacuum is at it’s highest. Air getting sucked through an intake gasket or a cracked vacuum fitting or line, can cause a whistle. There is also a vacuum reservoir for the power brakes that will hold vacuum for a short period of time (the idea is, if your engine quits while you’re moving, there will still be enough vacuum to have power assist to safety stop your vehicle). This reserve vacuum may be why the whistle hangs on after the engine is shut off.

    Diagnosis.

    Drive the vehicle under load. Simple hard acceleration or going up a steep hill should do it. The idea is to lug the engine (tall gear, low RPM). This will cause a normal drop in vacuum and the whistle should go away. If it does, then you know you’re dealing with a vacuum leak.

    Finding the leak.
    With the engine idling, disconnect one vacuum line as close to the intake manifold as possible (be very careful so as not to break old lines). If the whistle does not change, then put the line back on and move to another line that’s connected to the manifold. If the whistle stops, then put your finger on the connection you just unplugged the line from. If the whistle returns, then the problem is between your finger and the intake manifold. If the whistle doesn’t return, then the problem is somewhere along the line you just unplugged. Re-attach the line (the whistle should return) and follow the line to the next connection. Disconnect the line at that junction and see what happens to the whistle. Repeat the process, working your way down the lines until you identify the hose or component that is leaking.

    Happy hunting.
     
  4. Jun 12, 2020 at 3:21 AM
    #4
    captsolo

    captsolo New Member

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    My first thought was the PS pump. But could be a bad pulley (somewhere; AC, WP) on the belt. Engine sounds good. Not transmission or TC.

    To run a check, take the belt off and see if the sound goes away.

    How many miles you got on her?

    Ever try a stethescope?
     
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