vacuum question

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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, vacuum question in Past Cadillac Vehicle Discussion; 1990 Brougham. Is the vacuum system a closed system? Is a leak anywhere a leak everywhere? ohio boy...
  1. #1
    ohio boy is offline Cadillac Owners Member
    Automobile(s): 1990 brougham
    Join Date
    Jul 2012

    vacuum question

    1990 Brougham. Is the vacuum system a closed system? Is a leak anywhere a leak everywhere?

    ohio boy

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  3. #2
    csbuckn is offline Cadillac Owners Master
    Automobile(s): 84 Coupe w/500
    Join Date
    Jan 2008
    Olds 307? A leak at the back of the intake manifold will be a leak everywhere. I believe there are three different vacuum systems in the car but they all need a steady manifold vacuum. I believe emissions, hvac and engine accessories are all separate from each other. I could be wrong, emissions and accessories could be together.

  4. #3
    sven914's Avatar
    sven914 is offline Cadillac Owners Connoisseur
    Automobile(s): 1989 Brougham d'Elegance, 1985 Fleetwood Brougham *Coupe*
    Join Date
    Dec 2008

    Re: vacuum question

    On the 307, the emission controls system is tied into accessories like the ILC and vacuum brakes; the ILC helps stabilize the engine idle when the A/C compressor or alternator is causing a strain, and the vacuum brakes prevent engine run-on (dieseling) when the engine is turned off. The cruise control is mostly a stand alone system, but its vacuum source is spiced into the line going to the vapor canister.

    Basically, if you have a leak anywhere in the system, it will cause some decrease in performance. Also, if you have a leak in the system, you can be almost guaranteed that there is another leak somewhere else, and you should just replace all the vacuum lines.

    Here is a vacuum diagram:

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