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Do-It-Yourself Projects
Radiator Flush
By Tom Morr/
Printable version
Degree of DifficultyModerate
Estimated Time60 minutes
60 minutes
Drain the old coolant through the radiator's petcock. Capture the antifreeze in at least a 2-gallon bucket, and mop up any spills promptly. Antifreeze is toxic.
Drain Old Coolant
If the engine has drain plugs and they're accessible, remove them to release the old coolant that's trapped in the engine. (Some radiators only hold about 40% of the system's coolant.) Seal the plug's threads with Teflon tape or pipe dope before reinstallation.
Remove Drain Plugs to Release Old Coolant
Rusty or murky coolant isn't good. Scale and other particles can clog the radiator. This engine needs a serious flushing.
Rusty-Colored Coolant is Not a Good Sign
Flush/radiator-cleaning products are formulated to loosen rust deposits and other sludge. With all plugs and petcocks closed, add the product to the radiator, fill the system with water, and run the engine per the instructions on the bottle.
Add a Flush/Radiator-Cleaning Product to Loosen Rust Deposits and Other Sludge
Flush kits "back flush" the cooling system by reversing the direction of fluid flow through the block, heater core and radiator. The kit's T-fitting is spliced into the heater-inlet hose and accepts a garden hose. Flush until clear water emerges from the radiator neck.
The Flush Kit's T-Fitting is Spliced into the Heater-Inlet Hose
Clean the radiator's overflow reservoir then add the recommended amount of antifreeze (40%-70% depending on engine and climate) to the radiator and reservoir. Clean up any spills immediately.
Add the Recommended Amount of Antifreeze
Cooling-system additives include rust-inhibitors. Add them to the radiator before topping it off with tap water. If the system is really rusty, consider using distilled water, which has fewer minerals. Also, check the service manual about "burping" air from the system.
Add Cooling System Additives
If overheating is still a problem, consider adding a coolant additive that lowers the system's operating temperature.
Coolant Additive Can be Added to Lower the System's Operating Temperature
After driving for a few days, check the ratio of antifreeze to water with a hydrometer or test-strip, then adjust the concentration as necessary.
Check the Ratio of Antifreeze to Water with a Hydrometer or Test Strip
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