Coolant Flush
ModerateA coolant flush involves draining all the old coolant from the cooling system, flushing it with water or a cleaning solution, and refilling with fresh coolant. Over time, coolant loses its anti-corrosion and freeze-protection properties. A flush removes rust, scale, and contaminants that can clog the radiator and heater core.
Estimated time: 1-2 hours
Cost Breakdown
DIY (Parts Only)
$50 - $100
Professional Shop
$150 - $250
Prices vary by location, vehicle make/model, and shop rates.
Tools Needed
- Drain pan
- Funnel
- Pliers or screwdriver
- Coolant tester (refractometer)
- Distilled water
Step-by-Step Instructions
Allow the engine to cool completely. Never open the radiator cap or drain coolant on a hot engine.
Place a drain pan underneath the radiator and open the radiator drain petcock at the bottom of the radiator.
Once the radiator is drained, close the petcock and fill the system with distilled water. Run the engine with the heater on high for 10 minutes to flush, then drain again.
Repeat the water flush one or two more times until the drained water runs clear.
Close the drain petcock and fill the system with the correct coolant mixture (typically 50/50 coolant and distilled water) through the radiator cap or reservoir.
Start the engine with the heater on high and the radiator cap off to allow air bubbles to escape. Add coolant as the level drops.
Install the radiator cap once the system is full and air-free. Check the coolant level in the reservoir after the engine has cooled.
Tips & Warnings
- Use only the coolant type specified for your vehicle — mixing different coolant types can cause gelling and cooling system damage.
- Coolant is toxic to animals but has a sweet taste. Clean up any spills immediately and dispose of old coolant properly.
- If the old coolant is rusty or has oily residue, the cooling system may have a head gasket issue or internal corrosion.
- Check all hoses, clamps, and the thermostat while the system is drained — it is a good time to replace worn components.
Related OBD-II Codes
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Recommended Parts & Tools
coolant flush
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