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HT4100 4.1, 4.5, 4.9 Discussion, In search of a new/rebuilt vacuum pump... in Cadillac Engine Discussion; I know what you are talking about. If this thing has a leak, I'm guessing the entire system can't hold ...
  1. #31
    rootercycles is offline Cadillac Owners Member
    Automobile(s): 1985 Deville with 4.1
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    Re: In search of a new/rebuilt vacuum pump...

    I know what you are talking about. If this thing has a leak, I'm guessing the entire system can't hold a vacuum? Something to look at I guess. My Caddy is sitting down at a garage right now and they are trying to figure out why it won't start on occasion when it is hot.


  2. #32
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
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    Re: In search of a new/rebuilt vacuum pump...

    BTW I spent some time with a vacuum gauge taking readings today. With the engine off, the factory vacuum pump puts out a constant 15 hg of vacuum. When the vacuum pump disabled (fuse pulled) the engine alone also puts out 15 hg of vacuum. When the vacuum pump is running and the engine is idling, the vacuum load is approx 22 hg of vacuum.

    When driving, there is 15-25 hg of vacuum with the pump enabled and 5-25 hg when the pump is disabled (the low numbers come up when the engine is under acceleration load, while the high numbers are from deceleration). Based on this I would say that the pump is necessary to maintain a suitable vacuum floor of 15 hg.

    http://store.summitracing.com/egnsea...115+4294821918 has three after-market vacuum pumps that put out 20 or 25 hg. That is a little much for our application but I don't think it would hurt anything. I would be more inclined to use one of the 20 hg units.

  3. #33
    FrankC's Avatar
    FrankC is offline Cadillac Owners Member
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    Re: In search of a new/rebuilt vacuum pump...

    ehall --

    Interesting tests you made. Did you notice any difference in engine or ancillary device performance with the pump disconnected or connected?

  4. #34
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
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    Re: In search of a new/rebuilt vacuum pump...

    The only thing I noticed was that brakes were weaker with the pump disengaged. Cruise control and A/C still worked, although I think all of the cabin controls are on a separate vacuum harness (under the steering column according to one of the books).

  5. #35
    ehall's Avatar
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    Re: In search of a new/rebuilt vacuum pump...

    Here is some more info on one of the after-market pumps

    http://www.stainlesssteelbrakes.com/...ump+Kits&year=

    Builds 24" of vacuum.
    Dimensions: 8" L x 5" W x 7" H (approximate).
    Draws 10 amps.
    Flow rate: 1.53 cfm.
    Includes 12 volt vacuum pump, switching relay, vacuum line and control, mounting insulators and hardware.
    Turns on at 18" and shuts off at 23" of vacuum.
    24 hg is more than these old cars usually have. However it's nice that it has an integrated vacuum switch.

    Supposedly some of the early-80s Chevy Celebrity and other J-series cars have a pump with an integrated switch. I don't know if ours are supposed to have a switch or not, but I do know that mine's not working if it's supposed to have one.

  6. #36
    Crackillac's Avatar
    Crackillac is offline Cadillac Owners Member
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    Re: In search of a new/rebuilt vacuum pump...

    I know im 7 years late to the conversation but ive got the same BUZZIING. i ordered a Reman pump from Cadillac Kingdom on ebay, pugged it in and same Vibration. I is this thing supposed to run NON STOP? because this one does. and i know there is no way it would have been acceptable on a new luxury car even in 1986. I dont beleive there are any leaks as ive replaced just about every vac line i could find, Unless theres a problem in the brake booster, but the brakes function normally. Anyone have any luck finding the Newer model or Aftermarket Pump?

  7. #37
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
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    Re: In search of a new/rebuilt vacuum pump...

    It does run constantly.

    I ended up deleting mine and using a vacuum reservoir from one of the 4.5 models. The pump is only for the accessories anyway (cruise control, stuff like that), and the reservoir system on the later cars works just fine for that low demand.

  8. #38
    Crackillac's Avatar
    Crackillac is offline Cadillac Owners Member
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    Re: In search of a new/rebuilt vacuum pump...

    Ah I think my old Camaro had a reservoir thing on it, like a black plastic ball? (Makes sense now because it was busted open and the cruise never worked in that car lol)

    So how did you go about converting to the 4.5 reservoir set up and what all parts will I need to get?

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