Welcome to a new and informative section of Tomorrow’s Technician: “Tips from a Tradesman.” This month’s tip is finding a vacuum leak using a smoke machine. The engine used in this test is an LS version with your typical composite intake.
Several technicians struggle trying to find a vacuum leak. With today’s composite components and the methods of sealing them under the hood, a smoke machine is the safest and most accurate way to detect a vacuum leak. These machines were introduced to the trade about 25 years ago. Once you have seen one used or use one yourself, you’re hooked.
Along with the smoke machine, a 5 mil Nitrile glove is the other helpful component to use with a smoke machine. The glove makes a perfect seal and fits many different throttle body sizes. No more searching for the correct size plug and finding that you don’t have one. If you have a smaller orifice that needs blocked off, you can cut a finger off a glove and place it over the opening. This will help eliminate doubt of any unwanted seepage of smoke. When the smoke is introduced into the intake, the glove inflates showing there is presence of pressurized smoke. A bright light such as an LED is helpful to shine on the areas to detect the seepage of smoke.
Here you have a typical 12-volt smoke machine with the yellow plastic “block off” plugs.
Before you begin, the cover over the top of the intake needs removed.
Then, remove the intake tube from the throttle body.
Stretch a 5 mil glove over the throttle body.
Here you see the comparison between the “block off” plugs to the glove. The glove has a 100% no leak guarantee!
Place the smoke machine nozzle in the vacuum hose.
Start the smoke machine and you’ll see the glove inflate over the throttle body.
Here you can see smoke coming from the EGR tube, where the leak has been located.