Eiknujrac, you're correct the cooling system capacity is 10 quarts. It's necessary to open the engine block drain valves to drain most of the 10 quarts ... there is coolant in the auxiliary water pump, heater hoses and heater core. Unless you removed the thermostat or ran the engine long enough to open the thermostat during the flush only the radiator, not the entire system, got flushed. If so, I recommend removing the thermostat and flushing the cooling system again. Drain the engine block and radiator. Fill the system with tap water via a garden hose. Run the engine with the radiator cap off, radiator drain valve open and the garden hose in the top of the radiator matching the flow out the radiator drain valve so that the cooling system is full at all times, but not building up pressure. Run the engine for a few minutes until the drain fluid runs clear. Turn the engine off and drain the radiator and engine block and close the drain valves. Refill the system with a 50/50 mix of coolant and water and run the engine with the radiator cap off to evacuate any air in the system. Turn the engine off and reinstall the thermostat. Run the engine until it's up to temperature and check the fluid level in the expansion tank. Add a 50/50 mix up to the full mark and you're done.

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Fred Hoelzle