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  • T.A. Watson

How And Why To Flush Your Radiator

Updated: Jun 7, 2023

No one would argue that cars and trucks are complicated pieces of machinery that require a lot of maintenance. Just glancing under the hood reveals a wonderland of equipment and auto parts. And beyond what you can see, there are concealed parts within parts, totaling about 30,000 average auto parts in any given vehicle. Some parts get more respect than others, but the bottom line is that every part has a role to play in keeping your car or truck running smoothly.


A small auto part like a bad starter can put your car out of operation until the part is replaced. A damaged radiator, however, will not only bring your car to a halt by overheating, but it can cause serious and expensive damage to your car’s engine if it’s neglected. Regular maintenance and periodic radiator flushing are important preventative measures for your car’s overall health.


Why you should flush your radiator

Radiator coolant, a mixture of antifreeze and distilled water, is designed to protect and enhance engine performance by lubricating engine parts, preventing rust and corrosion, and maintaining free-flowing engine coolant. But no coolant lasts forever and although some formulations last longer than others, doing a coolant change, or radiator flush, drains the old, worn fluid and replaces it with fresh coolant that has a useful life of, generally, two to five years.


As the radiator flush drains away the old coolant, it also removes any rust, scale, corrosion, or debris that has gotten into the coolant over time. The entire cooling system, including water pump, hoses, and thermostat are cleaned during the process of flushing the radiator with a cleaning product followed by water rinsing to ensure every trace of old coolant is gone before new coolant is added. Fresh coolant restores the maximum protection for your engine, radiator, and cooling system from rust, corrosion, and overheating.


When you should flush your radiator

Following your car or truck owner’s manual for recommended service times is best to keep your vehicle at peak performance. The owner’s manual tells you everything from how to operate all the gadgets in your car to best-practices maintenance tips and preferred types of fluids, including engine coolant. If you’re not a “read the instructions from cover to cover” kind of guy or gal, at least review the section on recommended maintenance and plan scheduled maintenance to keep your car protected from unnecessary problems due to normal wear and tear. Ignoring regular auto maintenance is a great way to set yourself up for more expensive car repairs in future.


Your car’s make and model as well as the type of coolant you use will determine how often to flush the radiator. Conventional green coolant (ethylene glycol) which is recommended for many vehicles has a 30,000 miles or two years radiator flush schedule. Newer formulas that include organic acids have a useful life of up to five years or 150,000 miles before requiring a coolant change.


Other times a radiator flush is important would be when you buy a used car and don’t have its past maintenance log, if your radiator is filled with mixed coolants, or you want to switch to a different kind of coolant. Doing a radiator flush and starting clean is your best move going forward.

LKQOnline.com has all Years, Makes & Models for New and OEM Radiators

How to flush your radiator: DIY or see your mechanic

A radiator flush, considered by some a “relatively quick and straightforward procedure,” has multiple steps, all of which are important for a successful outcome. If you DIY, concerns include having the proper equipment (drain pan, storage container for used coolant, safety gear, jack, owner’s manual), space to perform the work, proper clean up, legal disposal of used coolant, and purchase of radiator flush cleaner and new coolant.


If you go to a qualified, certified mechanic, all of the above will be taken care of, plus you’ll have the added advantage of their expertise in checking all the hoses and parts of the cooling system as they do the radiator flush. Either way, here is a step-by-step guide for how to flush a radiator:

· Only do a radiator flush on a cooled engine and in a well-ventilated area.

· Wear rubber gloves and safety glasses as coolant/antifreeze is toxic and could cause serious damage if it gets in your eyes or on your skin.

· Apply the parking brake and jack up the front of the car and place the drainage pan under the radiator. The pan or bucket should hold at least two gallons of liquid, the old antifreeze you will drain off. A drop cloth underneath will catch any spills and make clean up easier.

· Lift the hood and inspect the radiator and hoses for any damage. If it needs repair or new parts, get that taken care of before you proceed with flushing the radiator.

· Take the pressure cap off the radiator and set it aside. Pull out the radiator plug (may need a socket wrench or screwdriver) and open the valve slowly over the bucket or pan. Completely drain the radiator (about two gallons of fluid) and replace the valve plug.

· Pour the old antifreeze into labeled, plastic jugs that can be taken to your local hazardous waste collection center.

· Clean the empty radiator with radiator cleaner and water poured into the radiator reservoir where you removed the pressure cap. Pour in the cleaner and one gallon of water and replace the cap. (Check out Best Radiator Flushes -- TheTruthAboutCars.com)

· Start the car and run it for about five minutes with the heater on full blast. This circulates the cleaner solution through the cooling system to remove every trace of old coolant.

· Turn the car off and let the engine cool for 15 to 30 minutes. Then, remove the pressure cap and radiator plug to drain off the cleaning/water solution. It will probably be dirty brown.

· Use just water at this point to rinse out the radiator, repeatedly using one gallon at a time, running the car with the heat on and then draining when cool, until it rinses clear. Then do a final distilled water flush before adding new coolant. Don’t use tap water for this final rinse, it contains minerals that will pollute your cooling system.

· Add your new coolant mix, car manufacturer recommended formulation and amount, to the radiator. Use a funnel and pour slowly as the liquid assimilates and fill to the radiator fill line. Start the car, heat on full blast, to facilitate pulling in all the coolant. When correct amount is added, replace the pressure cap, and let the car run for about 15 minutes.

· Turn off the car, let it cool, and check the coolant level one more time. If it’s below the fill line, add additional coolant until it’s full.


Don’t neglect the unsung hero that keeps your engine safe! Your radiator is crucial to your car’s performance, so any time you require radiator repair parts or a replacement radiator, LKQ Online can provide high-quality used auto parts as well as new aftermarket auto parts that will have your car or truck running like new. Trust LKQ for fast shipping, free standard warranties, guaranteed fit, and helpful customer service when you shop online.

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