7736850_004 Volvo.Penta MD21, AQD21

If using a commercial HD coolant/antifreeze which meets ASTMD4985: drain, clean, and refill the cooling system Every Year or 241 500 km (150,000 miles), whichever occurs first.Use of commercially available cooling system cleaners may cause damage to cooling system components. Use only cooling system cleaners that are approved for Caterpillar engines that have aluminum cooling system and engine components.DO NOT use a cooling system cleaner that contains tri-sodium phosphate. Tri-sodium phosphate will damage the aluminum components in the engine.
A good time to inspect the water pump, replace the water temperature regulator, and replace hoses is when your engine's cooling system has been drained.Drain the Coolant
1. Stop the engine and allow the engine to cool. Loosen the radiator filler cap slowly to relieve any pressure. Remove the radiator filler cap.2. Remove the cooling system drain plug(s) or open the drain valve. Open the cab heater valve to drain coolant from the cab heater. Remove the drain plug from the bottom of the water pump housing. Remove the drain plug from the bottom of the radiator. Allow the coolant to drain.
Dispose of used engine coolant properly or recycle. Various methods have been proposed to reclaim used coolant for reuse in engine cooling systems. The full distillation procedure is the only method acceptable by Caterpillar to reclaim the used coolant. Consult your Caterpillar dealer for information regarding disposal and recycling of used coolant.
For information regarding disposal and recycling of used coolant, call:Caterpillar Service Technology Group:Outside Illinois: 1-800-542-TOOLInside Illinois: 1-800-541-TOOLCanada: 1-800-523-TOOLClean the Cooling System
1. Flush the cooling system with clean water to remove any debris.2. Clean and install all drain plugs and/or close the drain valve(s).
Fill the cooling system no faster than 19 L (5 US gal) per minute to avoid air locks.
3. Fill the cooling system with a mixture of clean water and Caterpillar Fast Acting Cooling System Cleaner. Add .5 L (1 pt) of cleaner per 15 L (4 US gal) of cooling system capacity. Install the radiator filler cap.4. Start and run the engine for a minimum of 30 minutes with the coolant temperature at a minimum of 82°C (180°F). Stop the engine and allow the engine to cool.5. Loosen the radiator filler cap slowly to relieve any pressure. Remove the radiator filler cap. Remove the cooling system drain plug(s) or open the drain valve(s). Allow the cleaning solution to drain. Flush the cooling system with clean water until the draining water is clear. Clean and install all drain plugs and/or close the drain valve(s).Cooling Systems with Heavy Deposits or Plugging
For the following procedure to be effective, there must be some active flow through the radiator and the other cooling system components.Follow the same steps as outlined above, with the following modifications to steps 3 and 4:3. Fill the cooling system with a mixture of clean water and Caterpillar Fast Acting Cooling System Cleaner. Add .5 L (1 pt) of cleaner per 3.8 to 7.6 L (1 to 2 US gal) of cooling system capacity. Install the radiator filler cap.4. Start and run the engine for a minimum of 90 minutes with the coolant temperature at a minimum of 82°C (180°F). Stop the engine and allow the engine to cool.Fill the Cooling System
Refer to the Coolant Specifications for all information regarding coolant/antifreeze requirements. Refer to the Refill Capacities chart in this publication for the capacity of your engine's cooling system.
Fill the cooling system no faster than 19 L (5 US gal) per minute to avoid air locks.
1. Fill the cooling system with the recommended coolant/antifreeze mixture.2. Start and run the engine with the radiator filler cap removed. Allow the coolant to warm, the water temperature regulator to open and the coolant level to stabilize. Check the coolant level. Add coolant mixture if necessary to bring the coolant to within 13 mm (1/2 inch) below the bottom of the fill pipe or to the correct level on the sight glass (if equipped).3. Check the condition of the radiator filler cap. If the gaskets are damaged, replace the old radiator filler cap with a new radiator filler cap. If the gaskets are not damaged, use a 9S-8140 Pressurized Pump Group to pressure test the radiator filler cap. The correct pressure is stamped on the face of the radiator filler cap. If the radiator filler cap does not hold the correct pressure, install a new radiator filler cap.4. Start the engine. Inspect for coolant leaks and proper operating temperature.