Find those leaks

Tool Q&A addresses your questions related to the application of tools and equipment in your everyday work environment. So, if you’re curious about an application for a certain tool or equipment, please pass your question along to PTEN so we may use it in an upcoming issue.

This month, we answer questions related to the art of leak detection. New advancements in technology have brought about a new generation of leak detectors that surpass any previous types and their capabilities. Since accurate leak detection is essential to fixing it right the first time, you need to know how to perform this task accurately and reliably. 

Q. What are some common applications for using a smoke machine?

A. Smoke machines are rapidly emerging as an extremely effective way to find leaks in many different types of automotive systems. By introducing a calibrated amount of smoke into the affected system, you then look for visible signs of smoke leakage at potential leak points. One of the most common applications of a smoke machine is detecting EVAP system leaks. You can set the machine to release smoke at a given leak rate that matches specifications for identifiable leaks. Other applications include climate control systems, turbochargers and intercoolers, wind and water leaks, engine oil leaks, exhaust leaks, axle and differential leaks and vacuum system leaks.

Q. I have an older electronic refrigerant leak detector. Can I still use it to find leaks on today’s systems?

A. No. Older R-12 electronic leak detectors are not as accurate or sensitive as detectors that meet the current standard for leak detector performance, SAE J2791. SAE J2791 establishes minimum performance requirements for detectors used on motor vehicle A/C systems that contain R-134a. Among these requirements is a minimum of three, manually selectable leak-detection scales: 4 grams per year; 7 grams per year; and 14 grams per year. J2791 requires the detector manufacturer provide a list of common underhood chemicals that may result in false triggering of the detector.

Q. Are there any tricks to using an electronic leak detector so that I may find leaks more reliably?

A. There aren't any "tricks," but there are methods that can help chase down leaks more effectively. SAE J1628 establishes best practices for using electronic leak detectors that meet the J2791 performance standard. These two standards work hand-in-hand to provide best results. J1628 states:

  • Leak test when the system is not operating.
  • Ensure that the MVAC system static charge pressure is at least 50 psi, and that the ambient system temperature is a minimum of 59 degrees F.
  • Perform a visual inspection of the system, locating potential leaks by the accumulation of system lubricant or by visible hose/line damage.
  • Continue to check the entire system, even if one leak is detected.
  • Check the service valves both with the caps in place and removed.
  • Maintain a distance of 3/8" between the detector probe and the surface being checked; move the probe no faster than 3" per second.
  • Use the 7 grams per year setting to retest a leak found with the 4 grams setting, to help determine if the leak is of a repairable size.
  • Leak test an evaporator core by operating the A/C system blower on the high setting for a minimum of 15 seconds. Turn off the blower, and wait at least 13 minutes for any potential leaking refrigerant to accumulate in the evaporator case. Next, insert the leak detector probe into the blower motor resistor block opening, or the evaporator condensate drain hole (provided no moisture is present—it could damage the probe’s sensing tip), or the closest duct opening to the evaporator.
  • Leak test the service ports and also the repair area after a repair is performed.

Q. Are all UV leak detectors the same? How do I know the one I’m considering is well-suited to the task?

A. As with electronic detectors, there are SAE standards that apply to UV leak detectors and the procedures for using them. SAE J2299 sets the performance requirements for leak-detection dye injection equipment. SAE J2298 incorporates procedural best practices for using leak-detection dyes, including:

  • Use only dyes that meet SAE J2297.
  • Before injecting dye, look underneath the hood for a sticker indicating whether dye has already been installed. Alternately, remove the low-side service port cap and depress the valve stem for an instant to determine if dye is in the system. If dye is present, proceed to check for leaks.
  • Add dye according to the manufacturer’s instructions, provided that no dye was added previously to the system.
  • Place the identification label supplied by the dye manufacturer in a prominent place in the engine compartment (adjacent to the A/C charge label if possible).
  • Verify that the A/C system has a sufficient refrigerant charge as per factory specifications; then operate the system for a minimum of 15 minutes to circulate the dye.
  • Inspect the entire A/C system with a UV lamp with the engine off.
  • Trace the entire refrigerant system concentrating on leak-prone locations, such as hose-to-line couplings, service ports and connections. Check for evaporator leaks by illuminating the condensate drain hole. Only large leaks may be detected at this stage, due to the limited length of time the dye has been allowed to accumulate at any leak location. If a leak cannot be found, ask the customer to return in a week or more, after operating the A/C system as much as possible. This extended operating time should cause sufficient dye to collect at the point of leakage, enabling detection.
  • Continue to check the rest of the system even if a leak is found.
  • Verify any small leak by using an electronic leak detector as per SAE Standard J1628 to determine whether the leak is of a repairable size as defined by the vehicle or motor vehicle air conditioning system manufacturer. Some compressor shaft seal lubricant leakage may be normal for the system in question.
  • Remove any fluorescent residue using a cleaner approved by the vehicle or motor vehicle air conditioning system manufacturer after the leak is repaired. Although the use of fluorescent dyes is widespread in the A/C service industry, some manufacturers may prohibit using dyes, and others only permit specific dyes to be used. Always follow the manufacturer’s recommendations.

When using UV detectors, use care as ultraviolet light exposure can be hazardous to skin and eyes. To minimize UV exposure, wear UV-blocking eyewear, direct the light source away from your body and protect bare skin. Once again, the use of dyes must be acceptable by the A/C system and/or vehicle manufacturer, or meet the requirements of SAE J2297.

Stay tuned for more details about leak detection: It’s likely that a new refrigerant, HFO-1234yf, will replace R-134a. This will require some changes to both standards and leak detection equipment, so you’ll want to check back for the latest developments.

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