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Vacuum leak

Discussion in 'The Garage' started by Topdown, Dec 28, 2004.

  1. Topdown

    Topdown 1/2 ton status

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    Ok...

    Once again I seem to have a vacuum leak.

    I am running a 72 K5, TH350 trans, 350HO Deluxe crate motor around a year old, (maybe less), Q-jet...

    it idles like crap... tries to die when I get to stop lights. cold, warm, etc... idles like crap. I dont think my secondaries are opening either, but thats probably because the leak is bad enough that it wont pull then open. When I cup my hands over the carb it idles up like its choked so its sucking air from somewhere.

    I have tried starting fluid... it either isnt working for me or I have a vac leak on ever hose end, the base of the carb, the entire intake manifold, etc... I am leaning toward that method isnt working for me.

    thoughts? Help? Anyone want to come fix it for me for beer and pizza?
     
  2. ntaj*ep

    ntaj*ep 1/2 ton status

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    Could be leaking from under the intake in the lifter valley. Make sure the carb is bolted tight and your one way valve on the power booster for the brakes is operating correctly.
    Take a mechanics stethascope remove the probe so the open hose is left and run it across any area that could be leaking.

    Is this a consistant issue? Like it keeps poping up? Is it all the time or only warm?
     
  3. R72K5

    R72K5 Banned

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    connected a shop vacuum guage yet ?

    sound slike idle circuit may be fudged in the carb, unless timing is retarded too much

    check these things, let us know what timing and vacuum settings youre running

    good luck
     
  4. rerun93

    rerun93 Registered Member

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    does the exhaust smell rich of fuel?
     
  5. Topdown

    Topdown 1/2 ton status

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    constant
     
  6. Topdown

    Topdown 1/2 ton status

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    I dont know if the exhaust smells rich or not, I dont remember taking the time to smell it.
     
  7. Topdown

    Topdown 1/2 ton status

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    timing is set @ 10, was set before the issue started and is still sitting there. No idea on the vacuum setting yet
     
  8. Topdown

    Topdown 1/2 ton status

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    just another tidbit... I cant pull off vac hoses and create a vac leak that causes the truck to run worse. Just another indicator that its a vac leak
     
  9. ntaj*ep

    ntaj*ep 1/2 ton status

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    I say take a vac. reading at manifold port...
     
  10. sweetk30

    sweetk30 professional hooker Premium Member

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    vac leak info

    if you have a friend in the auto biz ask him to use the new smoke machine. 3-4 companys sell them man do thay work. we have one at work. you can check coolent ,vac, leaks and exaust leaks just about anything you can think of . the other day i did a p/s leak and found it up under the motor were i couldnt see it . what a time saver.
     
  11. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    If you have a vacuum advance distributor, make sure that the advance diaphragm isn't ruptured. I spent over a year searching for a small vacuum leak and was I shocked when I finally found it on the vac advance line...... :mad:
     
  12. Topdown

    Topdown 1/2 ton status

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    ok...

    I have replaced every vac hose on the truck now. (including the line down on the tranny)

    unhooked the trans and power brake booster lines and plugged them to test ... still have the problem. I am going to pull off every line and plug all the holes tomorrow morning. If I still have the leak, its a manifold leak.

    As it sits right now, when I spray starter fluid on the driver side intake/head the RPM increase. if I hold it and spray lots, the RPM increase more. So, I am guessing that its a manifold leak.
     

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