64 50... Leak detection with forming gas

Observe national regulations in all other countries!

Read and comply with the manufacturer's operating instructions provided with the special tool particularly with regard to accident prevention, health protection and environmental protection.

Only the basic procedure is described in the following! 

Certain user behaviors can lead to a loss of refrigerant from the refrigerant circuit even if there is no leak. This may occur if the customer has not used the air conditioning for a period of more than six months. This may cause O-rings to harden and refrigerant may escape. In this case, it will be sufficient to top up the refrigerant circuit and switch the air conditioning on for approximately 10 minutes while the engine is running.

Necessary preliminary work 

• If components of the refrigerant circuit are contaminated, clean the engine compartment. Otherwise, the sensor head of the leak detector will become contaminated.
  IMPORTANT: Notes on washing a vehicle with a high pressure cleaner:

  • Do not wash directly on gaskets and control units during engine washes.
  • A minimum distance of 30 cm must be adhered to for tires and tire valves.
  • A minimum distance of 30 cm must be adhered to for the soft top and painted parts.
  • Do not use if engine is still hot.
  • Do not exceed maximum water temperature of 60 degrees.
  • Do not spray directly onto cameras/sensors.
  • On electric or hybrid cars do not wash on high-voltage components.
• Remove center fresh air grille 
• Remove drive belt from A/C compressor
• Drain off air conditioning system 
• Fill the air conditioning system with forming gas
• Set pressure to 5 bar

To reach components of the refrigerant circuit with the leak detector, it may be necessary to remove the following parts, depending on the vehicle:

• Covers
• Trim panels
• Air duct
• Intake silencer
• Bulkheads

With some vehicles, the air flaps of the automatic air flap control (LKS) must be opened.

This is absolutely necessary to find certain leaks, such as in the area of the O-rings.

If no leak is detected, repeat the leak detection with 10 bar. 

Forming gas consists of 95% nitrogen and 5% hydrogen. The leak detector will detect hydrogen. If this is leaking from the refrigerant circuit even though the pressure remains, the leak detection bears no results.

Do not start  the engine during the entire procedure!

Fig 1: Overview Of Leak Detection With Forming Gas

Courtesy of BMW OF NORTH AMERICA, INC.

Notes for handling the leak detector:

1. Sensor head must always stand vertical to the surface to be tested.
2. Sensor head must always be aligned to the center of the point to be tested. Slowly guide the sensor head around the point (e.g. connection point, sealing surface, etc.).
3. The optimal distance (A) between sensor head and surface to be checked must permanently be approximately 1 mm, maximum distance (B) at points that are difficult to access approximately 5 mm.
4. Test speed may not exceed 2 cm per second.

Multiple leaks may be present in the refrigerant circuit.

Non-compliance will significantly reduce the efficiency of leak detection!

Fig 2: Overview Of Points In Leak Test Sequence

Courtesy of BMW OF NORTH AMERICA, INC.

Overview of points to be checked in test sequence: 

1. Capacitor: 

   Damage caused by stone chipping, etc. is the most frequent cause of capacitor leaks (1):

   1. Visual inspection in the area of the ornamental grille (2) and air inlet grille, center (3).
   2. Check damaged points first.
   3. Check the remainder of the capacitor.
      Fig 3: Identifying Ornamental Grille And Capacitor Leaks

      Courtesy of BMW OF NORTH AMERICA, INC.
2. Connection point capacitor - refrigerant line 

   Check the connection point between the connection at the capacitor (1) and refrigerant lines (2).

   Fig 4: Identifying Capacitor And Refrigerant Lines

   Courtesy of BMW OF NORTH AMERICA, INC.
3. Expansion valve: 

   Check the connection point between the expansion valve (1) and refrigerant lines (2).

   Fig 5: Identifying Expansion Valve And Refrigerant Lines

   Courtesy of BMW OF NORTH AMERICA, INC.
4. A/C compressor: 

   Check the following components on the A/C compressor:

   1. High-pressure connection
   2. Low pressure connection
   3. Pressure relief valve
   4. Radial shaft seal of the magnetic coupling: Turn the magnetic coupling several times by hand during the leak detection.
      Fig 6: Identifying A/C Compressor

      Courtesy of BMW OF NORTH AMERICA, INC.
5. Filler neck 

   Blow out the filler neck (1) prior to testing.

   Fig 7: Identifying Filler Neck

   Courtesy of BMW OF NORTH AMERICA, INC.
6. Refrigerant pressure sensor 

   Check the sealing surface between the refrigerant pressure sensor (1) and the refrigerant line (2).

   Fig 8: Identifying Refrigerant Pressure Sensor And Refrigerant Line

   Courtesy of BMW OF NORTH AMERICA, INC.
7. Refrigerant lines: 
   1. Perform visual inspection
   2. Check damaged points first.
   3. Check bending points at points marked with an arrow. Leaks occur especially frequently at these points.
   4. Check the remainder of the refrigerant line.
      Fig 9: Locating Refrigerant Lines

      Courtesy of BMW OF NORTH AMERICA, INC.
8. Evaporator: 

Compliance with the following settings is absolutely  required:

• Air recirculation function On
• Lowest blower speed
• Lowest temperature
• Set the air distribution to ventilation (air may only flow out of the center  fresh air grille)

Position sensor head (1) in air duct of middle fresh air grille (2) as illustrated and move slowly from inside to outside above and below air flap (3). Carry out this operation on the left and right fresh air grilles.

Fig 10: Locating Damaged Points And Bending Points

Courtesy of BMW OF NORTH AMERICA, INC.

In this case the expansion valve must be covered!

Following the completed leak detection:

• EVACUATE AND FILL HEATING AND AIR CONDITIONING SYSTEM