Detecting Vacuum Leaks

Searching for vacuum leaks is fundamentally the same as with air leaks, with one difference: the sound generated at the leak is stronger towards the inside of the system that generates it.  Fortunately, that remaining on the outside is strong enough to create a signal that can be picked up in some cases, several feet from the leak.

Remember that the size and the shape of the orifice, affect the intensity of the generated sound as significantly as the amount of air or gas rushing through it.  Therefore judgments on the actual size of the leak should be reserved until a more thorough inspection is made.

The AccuTrak® helps you find the location of the leak, and by reproducing the sound fluctuations, it gives you an indication of its rate.  Vacuum leaks sound the same as air leaks.

When checking for vacuum leaks in mechanical systems such as intake manifolds of automobile engines, much sound activity is created from valves and other components.  These sounds differ from leaks because they are rhythmic, i.e. they follow the engine motion, unlike leaks, which stay almost constant.  The same is true with mechanical vacuum pumps.  The nose cone may be necessary to help isolate other noises or to identify closely spaced leaks.  If the system can be pressurized with nitrogen or any other gas, you will find the leaks faster with only one Bar of pressure, (14.7 PSI) than trying to do the same with vacuum.  Simply because the sound is stronger on the outside of the system.

A technique that could be used, if the system permits, is a spray of distilled water.  Using a spray bottle to wet the suspect areas will increase the sensitivity of the detection.  The droplets, as they enter the system, explode and generate shock waves that the AccuTrak® can detect.  You may use alcohol or acetone, but the choice is yours and depends on system requirements and safety.


  • Move the instrument slowly around the suspect areas.
  • Use the nose cone with a piece of tubing.
  • Use pressure if the system permits it.