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Thread: Whistle sound from Valve Cover breather tube..Weird

  1. #1
    Van Enthusiast
    My Van(s):
    1986 LE
    Join Date
    Aug 2017
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    Whistle sound from Valve Cover breather tube..Weird


    I replaced my AC Compressor and ran the van up. After about 3 minutes is starts to whistle, almost like it was a belt squeak. It kinda sounded like it was in sync with the engine speed. Checked all belts, pulleys, idlers, etc. There was no noise coming from any of them. However what I noticed was when I turn the engine off the whistle did not stop, instead it continued for about 1 sec then slowly went away.
    So the next thing I did was get it to whistle again and open up the radiator cap, no change, then the oil cap, bang! it stopped. Then the PVC, no change, then the breather from the valve cover to the fuel manifold and it stopped. Then I plugged up the breather on both sides and it stopped. So by removing the manifold out of the picture it stopped, doesn't run as good but at least stopped.
    Checked all around the manifold for noise and could not hear a thing. I just cannot locate where it is coming from.

    Any ever have this issue?


  2. #2
    Van Obsessed
    My Van(s):
    88 4WD DLX 5spd
    Join Date
    Oct 2010
    Ontario, Canada
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    Re: Whistle sound from Valve Cover breather tube..Weird

    MT - Just wanted to say that its nice to know other people run into weird/strange/stupid things, just like me, almost makes me feel normal

    I don't have a clue what's going on and am having trouble envisioning your process but ....

    Whistling sounds have always ended up being vacuum leaks for me and a whistle that occurs after shut down then fades away, makes me want to look at all things vacuum. Brake booster, EGR, VSV's, dash pots...
    Get it making the noise and use a stethoscope to listen to each device and you should be able to narrow it down the source

    I've been chasing a suspected vacuum leak on Suzy for several years now, (recurrent lean code)
    I wont bore you with all the details, only that it has inhaled large sums of money with no solutions.
    It has a slightly lumpy idle, intermittent ac problems and throws intermittent lean codes.

    Due to C19 I haven't been out much, fired it up yesterday after being parked for 2 months and it starts whistling like Dixie
    It has never ever whistled before!
    Pulled the hood release and spent the next 20 mins trying to get the hood open (latch and hinges all seized!)
    By the time I got access the noise had stoped.
    My point being, while I had convinced myself I had eliminated all potential vacuum leaks, I must have missed something.
    Given that it passed all leak tests to date, I am contemplating the possibility off an internal leak, like a VSV that isnt fully closing....

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