Lessons on leak detection

In this issue's column, we cover your questions related to leak detection in various systems. State-of-the-art technologies continue to breed new solutions and approaches to chasing down pesky leaks. Let's see what piqued the curiosity of PTEN readers.

Q. I was at an air conditioning class this summer and heard the EPA approved a new refrigerant for auto A/C systems. Will our shop need yet another leak detector to trace leaks in these new systems?

A. THE USEPA formally listed HFO-1234yf refrigerant as an acceptable refrigerant back in March 2011. At this writing, the feds have not yet passed any regulations stating what's required to work on HFO-1234yf systems, which would impact A/C refrigerant handling equipment, refrigerant identifiers and leak detectors. However, the Society of Automotive Engineers (SAE) has published numerous new standards for working with HFO-1234yf refrigerant, in collaboration with the automotive industry. As part of this "suite" of new standards, SAE J2913 spells out the minimum performance criteria for electronic leak detectors to be used with HFO-1234yf. Electronic leak detectors meeting the performance criteria in the new SAE standard will have a label affixed, "Design certified by (name of testing laboratory) to meet SAE J2913 (with lettering in bold face)." If history is any indication, EPA will likely adopt the new SAE standards as the framework for regulations surrounding service on the new A/C systems. Since GM plans to use HFO-1234yf, in its 2013 models, you can bet on hearing something soon from EPA on new regulations.

Q. We'd like to use a dye-based detection system, but have concerns about the dye's effects on coolant color and integrity. Since we work on practically all makes and models, does this rule out using this kind of technology?

A. No, some manufacturers of dye-based systems are well aware of the potential issues caused by dyes when used for this purpose. Accordingly, they've concocted special dye formulations that do not affect coolant color nor integrity. When using dyes, always follow the manufacturer's recommended ratios to ensure you're using the proper amount of dye for the system being tested.

Q. We use dye detectors, but find that getting into cramped areas can be difficult with the ultraviolet lamp. Are there any tricks we can use to get around this limitation?

A. While you certainly can use a mirror to reflect the light into those tight spaces, you won't always have the room to use a mirror, either. For tight quarters, use one of the portable, flashlight-type detection lights. Using LED technology, they give you the utility of not only being able to detect dye at the source of a leak, but the light also doubles as a flashlight for other purposes.

Q. When choosing a dye for air conditioning leaks, are there any special considerations I should take into account?

A. Yes, make sure the dye you choose does not contain any solvents that may have a negative effect on the system. Solvents can impair the viscosity and lubricity of refrigerant oils, which could potentially cause damage to the compressor and other system parts. Always check with the manufacturer to make sure the dye is free of solvents.

Q. We get our share of cars with vacuum leaks, and we've had some comebacks due to missing a leak during a visual inspection. Is there a more positive way to find vacuum leaks?

A. One emerging technology that fits the bill perfectly for these types of leaks is called a smoke machine. When sleuthing out a vacuum leak, you feed artificial smoke from the smoke machine into the intake manifold, and then thoroughly inspect all potential leak points for escaping smoke. The smoke machine also works well when tracking down leaks in EVAP systems and HVAC controls. Some machines provide ultraviolet-light enhanced smoke to make leaks even more evident. This allows further discrimination of leaks, through use of a detection light.

Q. Our tool rep has a deal on electronic vacuum leak detectors. How do they work and are they effective?

A. Electronic vacuum leak detectors find leaks using ultrasonic technology. That is, they “listen” for the high-frequency characteristics that vacuum leaks produce, outside the spectrum of human auditory detection. Leak detectors with this type of technology produce an audible and visual indication when you're near a leak with the detector's probe. This sure beats trying to find a leak by sound, since you're typically trying to pinpoint a leak with the noise of the engine in the background. So yes, ultrasonic detectors can be extremely effective when chasing down vacuum leaks.

Q. We perform a lot of brake diagnostics and one of my techs asked about using dyes to detect hydraulic leaks. Do they work for this application?

A. Exercise caution here as dye-based leak detection technology is generally not intended for braking systems. For the most part, dye-based detectors usually work only in circulating systems. In other words, dyes typically work on systems where oil, coolant, refrigerant or other liquids or gases are continuously being circulated in a “loop.” With that said, new products are always emerging in the market, so always check with the manufacturer to see if they explicitly state their dye system can be used on automotive hydraulic braking systems.

Q. How do I know the refrigerant leak detector I'm considering is up to par with industry requirements?

A. If you're considering an electronic leak detector for R-134a systems, make sure it meets the minimum performance criteria spelled out in SAE J2791. Labeling on the detector should clearly state that the product meets the requirements of this standard. If there's any question, check with the manufacturer. Remember, the sensitivity of detectors meeting this standard work hand-in-hand with an established procedural standard for using the detector, SAE J1628. Similar guidance comes into play when choosing a dye-based detector. When looking for one of these, look for dyes that meet SAE standard J2297, and remember to affix a label to the system stating that a dye has been added. As with electronic detectors, using a compliant dye-based system works in concert with another SAE procedural standard, J2298.

Q. When using a dye-based detector for finding oil leaks, how long do I need to wait after adding the dye to the system before I begin checking for leaks?

A. After adding the dye to the engine, just allow it to circulate a few minutes with the engine running and you can begin searching for the leak right away. Remember that the ability to detect the leak will depend on the rate of the leak, and the amount of time that the dye circulates. Some leaks will be readily apparent in a short amount of time; others may take more time.

Q. After I've added dye to a system for leak detection, do I need to flush the system once repairs have been made?

A. No, approved dyes can remain in the system after a leak is fixed and will cause no harm. In fact, the dye still in the system can be used to verify repairs afterward. Always use dyes at the recommended ratio for the system they're being used in.

Q. We specialize in exhaust systems and frequently check for exhaust leaks during diagnosis. Our usual technique involves restricting the exhaust at the tailpipe and then listen for leaks. Is there a more effective way to look for exhaust leaks?

A. Yes, a smoke machine provides a simple and effective means of pinpointing exhaust leaks. Using an adapter cone at the tailpipe, you activate the smoke machine so that it fills the exhaust with smoke, Then, inspect all potential leaks points for escaping smoke, including pipe connections, manifold flanges, and others.

Q. Our collision shop faces leaks from sunroofs and general wind and water leaks from doors and windows. Any tips for taking some of the guesswork out of finding these problems?

A. A smoke machine or ultrasonic leak detector can help you pinpoint problems in these areas, possibly eliminating the need to drive the car or spray suspect areas with a hose. Simply apply smoke or pass the ultrasonic leak detector's probe near suspected leak points to find leaks in a lot less time.

Q. We use a dye-based detection system in our shop for finding coolant leaks, but it sometimes takes several attempts to find leaks. Is there anything we can do to improve our odds when isolating these types of leaks?

A. Yes, to help with your success, also use a cooling system pressure tester to emulate the pressures found in an operating cooling system. This may help push coolant out of weak spots in the cooling system, thus increasing the odds of finding a leak the first time out.


Thanks for looking to PTEN to help guide you with your tool and equipment choices. Keep your questions coming and we'll see you in the next issue.