Checking The Antifreeze Content Using A Refractometer

Information 

• The following diagram shows the scale used by Leitenberger 
• The scales can vary, depending on the manufacturer, observe the operating instructions 
• Use the "ETHYLENE" scale for Porsche coolant. 

1. The correct antifreeze content is given on the ETHYLENE scale
   Fig 1: Identifying Refractometer Scale

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.

   Position	Designation	Explanation
   -A-	Scale for propylene-based coolant	Do not use the scale for engine types M96/03, M96/05 and M97/01
   -B-	Scale for ethylene-based coolant	Use scale for 997 engines
   -C-	Scale for battery acid	The charge state of a battery can be checked here. The figures indicate the gravity of electrolyte. The battery must be recharged once the charge drops below 1.20.
   -D-	Scale for alcohol-based windscreen cleaner	The freezing point of the windscreen cleaner can be read off here.
   -E-	Light/dark limit	In conjunction with the points of intersection of the relevant scales, it specifies the value to be established
   -F-	Waterline	The light/dark limit must be located here when sprinkled with distilled water

2. Using a pipette, take a sample from the coolant expansion tank. Trickle a few drops onto the test surface of the refractometer.
   Fig 2: Identifying Coolant Sample

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.
3. Close the light-diffusing lens. A closed liquid film must form.
   Fig 3: Identifying Closed Refractometer Lens

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   Information 

   • The following table specifies how much coolant must be replaced by pure coolant in order to adjust the freezing point to -37 °C. 
4. Hold the refractometer against a bright light source. A clear light/dark limit emerges. The point of intersection between this line and the display scale marks the freezing point of the coolant. A freezing point that is too low must be adjusted according to the table below

   Measured antifreeze content in °C	Pure antifreeze quantity to be added (in liters)
   - 5	9
   - 10	8.5
   - 15	7.5
   - 20	7.0
   - 25	5.0
   - 30	3.5
   - 35	1.5