Air cleaner cold start door

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HT4100 4.1, 4.5, 4.9 Discussion, Air cleaner cold start door in Cadillac Engine Discussion; Anyone owning a Seville or Eldo in the late 70's to middle 80's should verify the vacuum operated door in ...
  1. #1
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003

    Air cleaner cold start door

    Anyone owning a Seville or Eldo in the late 70's to middle 80's should verify the vacuum operated door in the air cleaner snorkle is in fact, open when the engine is at operating temperature. My 84 remained shut unless the engine was off! Its supposed to slowly open to allow heated exhaust manifold air to warm up the throttle body on a cold engine start. Its very important in cold weather climates, but here in California it rarely gets below 50 degrees. So, I installed a small check ball in the vacuum hose to the door, now the door remains open always. My car was getting 21 MPG at 70 MPH on cruise control. Now with this door open, it gets 23 MPG!

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  3. #2
    awadecki is offline Cadillac Owners Enthusiast
    Automobile(s): 76 Eldo (54k), 76 Eldo (52k), 78 Eldo (9k), 85 Deville (43k)
    Join Date
    Jun 2005

    Re: Air cleaner cold start door

    True enough. However, the door is supposed to stay closed until the internal air cleaner temperature approaches 135 degrees Fahrenheit--quite hot.

    When it's 40 degrees or below outside, my ThermAC door stays closed most of the time, but this is how it should operate.

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