The 5 Most Common Errors in Automotive Leak Testing

New ebook from INFICON covers leak testing methods and applications in the automotive industry.

Leak locating on an engine using a hydrogen leak detector.

Leak locating on an engine using a hydrogen leak detector.

Millions of leak tests are conducted each year in the automotive industry. Errors in testing—such as contaminated test pieces or unnoticed temperature fluctuations—can be costly if they go undetected.

INFICON, a producer and supplier of leak testing equipment, recently released a free ebook entitled, Leak Testing in the Automotive Industry: A Comprehensive Guide to Leak Detection.

In addition to a slew of information on the various leak testing methods and their applications, the ebook includes a “Top 10” list of common errors in leak testing in the automotive industry.

Read on for our top five picks from INFICON`s list:

1) Wrong Test Method

Although it’s popular, the bubble test method is by no means conclusive. A tester might not see any bubbles and assume there’s no leak, but—as the saying goes—absence of evidence is not evidence of absence.

The essential criterion for determining whether a particular leak test is suitable for a particular application is the test’s leak rate.

2) Wrong Point in Time for Testing

Leak testing on a GDI engine using robotic helium sniffing.

Leak testing on a GDI engine using robotic helium sniffing.

It’s important to consider the best point in the production process for leak testing. For example, it’s best to check the tightness of a transmission case before the transmission is assembled.

If the housing fails in the final test and has to be ejected, then all the work that went into assembling the transmission was for naught.

3) Disregarded Temperature Influence

Temperature fluctuations are particularly problematic for integral leak tests which use pressure decay or differential pressure measurement.

Even small fluctuations can change the measurable leak rate by orders of magnitude. These will also affect the expansion behavior of the material being tested, which can in turn influence the size of a leak. 

4) Not Knowing What is Being Measured

Leak locating on an engine using a hydrogen leak detector.

Leak locating on an engine using a hydrogen leak detector.

Leak test rates are sometimes specified for air, which has a slightly lower dynamic viscosity than helium. Thus, if the leak rate is specified for air but testers use helium, then they must use proper conversion data to provide a more precise leak rate. This must also be taken into account when interpreting leak rate results using diluted helium mixtures.

5) Neglected Maintenance

If a test station goes days or even weeks without registering a leak, then you either have superb production quality or a malfunctioning test system. Leaking tracer gas lines could be preventing correct measurements in the test chamber and patching them with Teflon tape is not an adequate solution. Helium can escape through porous Teflon tape, leading to further accuracy problems.

Errors in a test system can be identified by regularly checking the system with a reference leak, such as a glass capillary or metal squeezed to a narrow point. However, the latter will vary in leak rate depending on temperature and pressure, which is why glass capillaries are the better option.

To read about other common errors in automotive leak testing download INFICON`s free ebook here.

For more information, visit the INFICON website.

Written by

Ian Wright

Ian is a senior editor at engineering.com, covering additive manufacturing and 3D printing, artificial intelligence, and advanced manufacturing. Ian holds bachelors and masters degrees in philosophy from McMaster University and spent six years pursuing a doctoral degree at York University before withdrawing in good standing.