How to find Vacuum Leaks

Discussion in 'Technical Q&A' started by tfrancis, May 16, 2004.

  1. tfrancis

    tfrancis Karting

    Nov 3, 2003
    Memphis, TN
    My 328 GTS has developed a high pitch whistle. I just rebuilt the engine and that is the only thing holding me up. The engine starts and runs but it's not correct due to the vacuum leak. Below are the responses I've received so far on how to find the leak.

    1. Use a heater hose. Hold one end up to your ear and move the other end around the engine.

    *** This seems pretty difficult.

    2. Spray carburetor cleaner around different connections and seals.... listen for the engine to revive up or down.

    *** Also seems pretty difficult if you trying to find a pin hole.

    3. Buy a smoke machine and fill the plentum. Where ever you see the smoke come out is the leaks location.

    *** I priced one at $1095.00.... just not pratical.

    Anyone know of the best way or is sending it to a shop the best thing? I don't have a ferrari mechanic in our area but maybe other dealerships would have the equipment.

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  3. tbakowsky

    tbakowsky F1 World Champ
    Professional Ferrari Technician Consultant

    Sep 18, 2002
    The Cold North
    Full Name:
    During the course of your rebuild, did you remove any emissions related components? Specificly the emulsion tubes that screw into the cylinder heads just above the exhaust ports?
  4. Smiles

    Smiles Moderator
    Moderator Owner

    Nov 20, 2003
    Pittsburgh, PA
    Full Name:
    Matt F
    Surprisingly, Sears has a very nice stethoscope in the Craftsman tool department. It's pretty cheap, but it works well for finding odd sounds. I hope that helps.

  5. tfrancis

    tfrancis Karting

    Nov 3, 2003
    Memphis, TN

    No I didn't remove any emulsion tubes. My first guess would be the vacuum lines under the Plentum. There are 8 of them that attach from the manifold to an Air Delivery Pipe. Realisticly it could be coming from many different areas so I need something that can pin point the problem.
  6. ric1241

    ric1241 Rookie

    Mar 6, 2004
    A method often used for very small leaks is to spray water around the suspicious area. The reduced pressure at the leak will evaporate enough water to drop the temperature and form a tiny ice plug. This should change the noise you hear or if using a gauge show an improvement in the vacuum.
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  8. Peter

    Peter F1 Veteran
    Rossa Subscribed Owner

    Dec 21, 2000
    B.C., Canada
    I'll second that. Its how I found the leaks around the throttle shaft bearings on my carbs...
  9. fatbillybob

    fatbillybob F1 World Champ
    Consultant Owner

    Aug 10, 2002
    If you rebuilt the engine why not use new vacum hoses? Sorry...I'm not trying to be a smart A
  10. tfrancis

    tfrancis Karting

    Nov 3, 2003
    Memphis, TN
    I did use new vacuum hoses. A leak like this could be very difficult to find I imagine.
  11. Wasco

    Wasco Formula Junior

    Dec 9, 2003
    Full Name:
    I have used the " Spray starting fluid and listen for the increase in RPM's" many times on v-8 gas and diesel engines with pretty good success.
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  13. speedball

    speedball Formula Junior

    Mar 29, 2004
    Pasadena Area
    Full Name:
    Scot Anderson
    I second this method ...... that is if it's a sizeable leak ... you'll hear the difference when it starts sucking starter fluid. Just don't blow yourself up thanks to some sparking plug wires!!!

    But I've also had very good success with a stethoscope finding a multitude of issues .... I use the Sears model mentioned .... it's amazing what sounds you can isolate and pinpoint using one of these.

    Good luck.
  14. AR!

    AR! Formula Junior

    Apr 8, 2004
    Berlin, Germany
    There are special foam building additives at cheap prices. Even minor leaks will cause a lot of easy visible foam. I used to use them when I was assembling pneumatic devices in vacation during my time at the University.

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