MAINTENANCE AND LUBRICATION 251 Refilling the Cooling System Close all drain cocks and fill with the proper coolant mixture. Run engine with the pressure cap removed until operating temperature is reached and the thermostat opens. Recheck level and add coolant if required. Run the engine long enough to be sure the system is free of air and has the correct amount of coolant.
Protecting the Cooling System
CAUTION The concentration of ethylene glycol or propylene glycol in the cooling system must be checked with a refractometer prior to traveling or operating in areas where subfreezing temperatures may be encountered. When adding antifreeze to the system, run the engine for 20 minutes before checking with a refractometer. Note: Your chassis is currently supplied from the factory with engine coolant protection to –23°C (–10°F). Optional coolant protection to –40°C (–40°F) is also available. Ethylene glycol or propylene glycol-based antifreezes are both approved for all MACK engines. All ethylene glycol and propylene glycol coolants must be low-silicate antifreezes which meet ASTM4985 test (GM6038M SPEC) criteria. These antifreezes are sometimes referred to as heavy-duty diesel coolants. Passenger car coolants do NOT meet this specification. Be sure to maintain the required level of antifreeze protection for anticipated winter temperatures in your area of operation. A 40% to 60% concentration of antifreeze is required for MP engines, regardless of application, geographic location or ambient air temperature.
CAUTION Do NOT exceed a 60% concentration of antifreeze to water. A higher percentage of antifreeze will not increase protection. Concentrations over 60% adversely affect freeze protection and heat transfer rates. Note: Propylene glycol should be checked with a refractometer.
