How to Flush Your Car's Cooling System

How to Flush Your Car's Cooling System

Regularly flushing your radiator is another vital element of car maintenance. Your car's cooling system protects it from the extreme heat generated by the engine and keeps the engine itself operating within the proper temperature range. Keeping the cooling system free of rust, buildup and contaminants will help keep it and your engine in top working condition. You should flush your radiator once every two years unless your owner's manual recommends otherwise.

 

What You'll Need

 

1-2 gallons of antifreeze (Be sure to consult your car's manual to confirm refill volume and the specific kind of antifreeze your car calls for. Your owner’s manual will also contain step by step instructions for your particular vehicle.)
1-2 gallons distilled water
A drainage pan or bucket
A garden hose with a nozzle
A pair of work gloves (preferably waterproof)
A soft bristle nylon brush
A bucketful of sudsy water
Safety goggles
Sealable container for proper storage of old coolant.
Before you get started be sure to read the instructions (and warnings) on the new coolant packaging.

 

Step 1 - Get Started

 

First and foremost, make certain that your engine is cold. A hot engine means hot coolant under very high pressure trapped in the radiator - and possibly a severe scalding when you remove the radiator cap. NEVER REMOVE A HOT RADIATOR CAP!

 

Step 2 - Clean the Radiator

 

Raise and securely fasten the hood to avoid accidental slippage. Remember, when working under the hood, keep an eye out for sharp edges on the radiator and fan blades. Then use your nylon brush and sudsy water to gently scrub away the dead insects and debris that have collected on the radiator grill. Be sure to scrub in the direction of the radiator fins and not against, as the metal is fragile and can easily be bent out of shape. Once the grill is clear, direct a gentle stream of water from the hose over it to ensure that all debris is completely gone.

 

Though you only have to flush your radiator once every two years, it's a good idea to clean the radiator grill every 12,000 or so miles.

 

Step 3 - Place the Drain Pan

 

Proper drainage of the used coolant is very important. Coolant is highly toxic but has a sweet smell that's attractive to children and animals. It should not be left to drain unattended and should never be allowed to drain into the ground. Make sure that the pan you use won't be used for any kitchen purposes - a disposable pan is ideal. Slide it into place under your car and center it under the radiator's drain valve (also known as a petcock).

 

Step 4 - Check the Radiator Cap

 

The radiator cap acts as a lid for the radiator, sealing and pressurizing the coolant within to keep the engine cool. The coolant pressure varies from engine to engine, and the pressure rating is indicated on the top of the cap itself.

 

A radiator cap consists of a spring coil stretched between a wide, flat metal top and a smaller rubber seal on the bottom. The tension between the spring and the rubber seal is what enables the cap to maintain pressure, so if it is easy to compress the two, the cap is worn out and should be replaced. Another sign indicating that you should replace the cap is rust or drying of the rubber seal. In general, the cap should be replaced at least every two years, so you may want to make it part of your routine when flushing the radiator. Remember, there are different caps for different pressure ratings, so always keep the rating number in your car's records.

 

Step 5 - Check the Clamps and Hoses

 

The next step is to check the radiator's hoses and clamps. There are two hoses: one at the top of the radiator and one at the bottom. The radiator must be drained in order for the hoses to be replaced, so checking them before you flush the engine is always a good idea. This way, if you find signs that the hoses are cracked or leaking or the clamps look rusty, you can change them before refilling the radiator. A soft, mushy consistency is a good indication that you need new hoses.

 

Step 6 - Drain the Old Coolant

 

The radiator's drain valve (or petcock) should have a handle that makes it simple to open. (Side note: Some engines have drain plugs on the engine and the radiator too. Again, consult your owner's manual to figure out what you're dealing with.) Simply unscrew the petcock (while wearing your work gloves - coolant is toxic) and allow the coolant to flow out into the drain pan you placed underneath your vehicle. Once all the fluid has drained, replace the petcock, and funnel the used coolant into the sealable container you have set aside. Then place the drain pan back under the petcock.

 

Step 7 - Rinse the Radiator

 

Now you're ready to do the actual rinsing! Simply take your garden hose, insert its nozzle into the fill spout of the radiator, and let it run until full. Then open the petcock, and let the water drain out into the pan. Repeat until the water runs clear and be sure to funnel all the water used in the rinsing process into sealable containers, as you did with the used coolant. At this point, you should replace any worn clamps and hoses, if needed.

 

Step 8 - Add Coolant

 

The ideal coolant mixture is composed of 50 percent antifreeze and 50 percent water. Distilled water should be used in the formula, as it is free of the minerals in tap water that could denature the coolant mixture and prevent it from properly doing its job. Most radiators will hold roughly two gallons of fluid, so it should be easy to judge the amount you will need to use.

 

Many cars have separate overflow/fill reservoirs, located away from the radiator itself. If your car has one, you should only top off and fill via these reservoirs. Again, if you have any questions, look at your owner's manual.

 

Step 9 - Bleed the Cooling System

 

Finally, it will be necessary to bleed out the pockets of air that may have settled in the cooling system. Start your engine with the radiator cap off (to avoid buildup of pressure) and let it run for approximately 10 minutes. Then turn on your heater, and turn it up to hot. This will circulate the coolant and allow any trapped air along with it to dissipate. Once the air is released, add a little more coolant, but be careful; the air releasing from the radiator can bubble up and be quite hot.

 

Then simply replace the cap and wipe off any excess fluid with a rag.

 

Step 10 - Clean Up and Disposal

 

Check for any leaks or spills from the petcock, dispose of rags, old clamps and hoses and your disposable drain pan. Now you're almost good to go.

 

It is just as important to properly dispose of used coolant as it is to dispose of used oil. Once again, the smell and color of used coolant makes it especially appealing to children, so don't let it sit around long. Transport those containers without delay to the nearest recycling center that handles hazardous materials.

 

One final note: Keep an eye on your coolant level. Check it a day or two after a refill. Check it again in a week, and then about once a month after that.

 

Wash time! Scrub hands (and any other body part the antifreeze might have touched) with soap and water. Trust me, you'll want to get this stuff off you as quickly as possible!

 

These handy tips on how to flush your cooling system were brought to you by Castrol Motor Oil.