dropping rpm when brake
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Cadillac Catera and Cimarron Forum Discussion, dropping rpm when brake in Past Cadillac Vehicle Discussion; had this problem over a year now (( time to time when i brake and stop my rpm dropping to ...
  1. #1
    JohnJJO's Avatar
    JohnJJO is offline Cadillac Owners Fanatic
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    dropping rpm when brake

    had this problem over a year now ((
    time to time when i brake and stop my rpm dropping to 200 or so, usually happened when im preforming stop and hold my brakes longer then usually, like if u coming to red light, 200 rpm remains for like 1 second or 2 and then rmp raise to normal 500

    HELP

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  3. #2
    JohnJJO's Avatar
    JohnJJO is offline Cadillac Owners Fanatic
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    Re: dropping rpm when brake

    Any Idea?????

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    gvjv3 is offline Awaiting Email Confirmation
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    Re: dropping rpm when brake

    Come on?, someone out there must have had this problem and fix it, I have it too, but have no idea ether, any suggestions?

    Thank You

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    jupiter57 is offline Cadillac Owners Member
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    Re: dropping rpm when brake

    Not on a Catera, but I had the same thing happen years ago.
    It was a vacuum leak, related to the brake booster, can't remember if it was the check valve, hose, or booster.
    If I remember correctly, somehow, when you applied brake, the vacuum would go to "uncontrollably open"(?)
    Think I had to replace the booster due to a vacuum leak.

    Regardless, it sounds like a Vacuum leak to me, and the reason it appears while braking leads me to advise you to start at the brake Booster.

    Might try plugging the Vac. line to your brake booster first, then isolate each seperate vacuum line until you find the culprit.

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    gvjv3 is offline Awaiting Email Confirmation
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    Re: dropping rpm when brake

    ok what is a brake booster? and where is it located?

  7. #6
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    It's the large, round component between the master cylinder and firewall. Inside, is a large diaphragm, that uses engine vacuum to provide power brake assist.

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    gvjv3 is offline Awaiting Email Confirmation
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    Re: dropping rpm when brake

    OK, got it, so how does that, have to do with engine RPM dropping up and down sometimes, I can,t see that its even connected to the engine, if there was a leak in the vacuum there, then it would effect the braking system and not the RPM right?

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    gvjv3 is offline Awaiting Email Confirmation
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    Re: dropping rpm when brake

    opps

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    JohnJJO's Avatar
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    Thread Starter

    Re: dropping rpm when brake


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    gvjv3 is offline Awaiting Email Confirmation
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    Re: dropping rpm when brake

    opps

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    98Geldog is offline Cadillac Owners Fanatic
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    Re: dropping rpm when brake

    Maybe IAC or TPS. As far as I know would cause idle problems.

  13. #12
    JohnJJO's Avatar
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    Re: dropping rpm when brake

    in my case it started to do way more now, approx. every fifth stop or so....
    According to my research it related to air lost due to broke mane rubber seal in booster, i personally swap twice throttler body in pass year (got used from junk ward) they both worked the same, (guys IAC and TPS its one unit for 2000 sport, call "Throttler body" its $400 peace). that's not the problem!!!!. Brake booster $100. i would personally replaced next day, but i have All Data when i looked on procedures... i change my mind to do it, it's just to mush to do

    so any idea?
    Thanks

  14. #13
    98Geldog is offline Cadillac Owners Fanatic
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    In my 2000 the IAC is mounted to the TB at the rear by the firewall it's got a couple vaccum lines connected to it. I have a similar issue, the car idles high at start cold or hot at around 250-300 and takes at least 1 minute to idle down and even then it stays above 1000 until I take off but while driving it fine. this also causes a hard shift. On a kinda warm day I will try to clean the IAC and replace all the vacuum lines.

  15. #14
    gvjv3 is offline Awaiting Email Confirmation
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    Re: dropping rpm when brake

    nevermind

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    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    .....You COULD put in a little effort, and find the meanings yourself. There's a sticky right here on these forums:
    http://www.cadillacforums.com/forums...-acronyms.html

    Or GOOGLE IT.

    Or at very least, just ask nicely.

    The members here are not getting paid, and are not required to walk you through everything.

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