Recommended Coolant Water Quality
Water used in the engine cooling system must be soft water. The water quality must meet the following requirements:
Water quality should meet with recommended limit, however, within limit is acceptable.
Table 4-3: Water Quality Standards
| Parameter | Unit | Recommended | Limit to Avoid Scale Formation | Limit to Avoid Corrosion | Main Adverse Effect |
| pH (25°C [77°F]) | — | 6.5 to 8.5 | < 9.0 | > 5.0 | Scale and Corrosion |
| Electrical Conductivity (25°C [77°F]) | µS/cm | < 250 | < 400 | — | — |
| Total Hardness | CaCO₃ ppm | — | < 170 | — | — |
| M Alkalinity | CaCO₃ ppm | — | < 70 | — | — |
| Chlorine Ion | ppm | < 100 | < 150 | > 50 | — |
| Sulfuric Acid Ion | ppm | < 10 | — | — | — |
| Silica (as SiO₂) | ppm | < 50 | — | — | — |
| Evaporation Residue | ppm | — | — | — | — |
Note: Figures in parentheses are the standard value. In addition to the items specified above, turbidity is specified to be below 15 mg/liter.