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Short Summary
Main recommendation: Flush a car's cooling system by draining the old coolant when the engine is cold, running distilled water with a chemical flush for about 10 to 15 minutes of driving, draining again, then refilling with a 50/50 antifreeze mix plus an anti-rust sealer and protector. The video demonstrates this on a 2000 BMW 540i, with a 3-gallon system capacity.
Key Points
- Work only on a cold engine, because the cooling system is pressurized and hot coolant can spray out when caps are loosened or hoses are disconnected.
- The radiator petcock (its drain plug) is usually in a bottom corner of the radiator; drain the old coolant into a disposable aluminum pan.
- Run the car with distilled water and a chemical flush to clean the system, and watch the temperature gauge and heater output to catch trapped air.
- After draining the flush water, refill with 50/50 antifreeze, adding an anti-rust sealer additive and running the engine to purge air.
- Check the owner's manual for the correct antifreeze type before buying.
Details Worth Noting
- Concrete instructions:
- Wait until the coolant is cold (in the blue area of the gauge or below) before touching caps or hoses.
- Locate the radiator petcock at the bottom corner of the radiator and unscrew it to drain the coolant into a pan. The BMW was low enough that it was not jacked up.
- Collect the old coolant and dispose of it properly so animals cannot drink it; auto parts stores, town recycling centers, and similar places accept it.
- Reinstall the drain plug and tighten it fully before refilling.
- Fill the reservoir with distilled (not filtered) water using a funnel; this system takes 3 gallons. Then start the engine and add the rest of the water so the water pump pulls it in and purges air.
- Add the chemical flush, then drive for at least 10 minutes (the host drove about 15). Watch the temperature and make sure the heater blasts hot; lukewarm heat suggests air in the heater core or too little water.
- After the drive, let the engine cool, remove the reservoir cap so draining flows faster, and drain the water. Restart the engine briefly to push out remaining water, then reinstall the drain plug.
- Refill with three one-gallon jugs of 50/50 antifreeze, adding the anti-rust sealer partway through. Turn the jug sideways to pour smoothly. Run the engine with the heat on until the level reaches the top.
- Drive again, confirm heater output and that the gauge sits at its normal midpoint (the host's reading was shown as 106, though normal operating temperature is well below that in reality, and it is likely meant as 106°F or a gauge marking, not a literal 106°C coolant temperature).
- The host notes that an old engine may develop leaks from flushing, which is why the sealer additive is included.
- A small amount of residual water is acceptable, but too much will leave the water-to-antifreeze ratio off 50/50.
- The video's closing tip was to check the weather before starting an outdoor project.
Bottom Line
A cooling system flush is a manageable DIY job if the engine is cold, the flush water runs clean, and the final mix is a correct 50/50 antifreeze blend, verified by heater output and a normal temperature reading.
