Should the manifold overpressure relieve valve be hissing?
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Should the manifold overpressure relieve valve be hissing? in Past Cadillac Vehicle Discussion; Greets, Like the title says, should the manifold overpressure relieve valve be hissing? After changing out a starter motor my ...
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    DJSG3 is offline Cadillac Owners Fanatic
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    Should the manifold overpressure relieve valve be hissing?

    Greets,

    Like the title says, should the manifold overpressure relieve valve be hissing? After changing out a starter motor my car developed an idle problem and after testing pretty much everything else involved the only thing I've noticed is a hissing sound coming from that area. Using a tube to my ear to isolate the sound, its only present when I'm at the front side and center of the manifold. If I move to either corner sound goes away.


    DJSG3

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    basscatt's Avatar
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    Re: Should the manifold overpressure relieve valve be hissing?

    should the manifold overpressure relieve valve be hissing
    NO -

    you could use carb cleaner to verify/find a vacuum leak -

    with the engine running - spray it around the suspect area -
    if the idle speed changes - you found a leak -

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    Ranger's Avatar
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    Re: Should the manifold overpressure relieve valve be hissing?

    If it's hissing, it's not seating properly and you have a vacuum leak. You may be able to clean and reseat the seal.




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    DJSG3 is offline Cadillac Owners Fanatic
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    Re: Should the manifold overpressure relieve valve be hissing?

    Greets,

    Turned out not to be the valve but the piece the valve sits in. It apparently loosened when disconnecting/reconnecting that vacuum line right below the fuel rail. Turned it as far as the rail would permit and then put some silicone caulk along the screw edge of the whole assembly, pushed it in with a putty knife, let it sit for 12 hours and then reassembled. Idle is now back to normal.

    DJSG3

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