Flushing and replacing engine coolant is an important maintenance task that helps keep your engine running at the right temperature and prevents corrosion and overheating

As coolant ages, its protective properties diminish; most automakers suggest a full flush and refill every 2–5 years based on driving conditions and coolant type

Follow this comprehensive guide to perform a safe and thorough coolant flush and refill

Never attempt this procedure while the engine is still warm or running

Never open the coolant system while the engine is hot or running

The pressure and heat can cause boiling coolant to spray out, which can cause serious burns

Allow a minimum of 60 minutes for cooling, but performing this in the early morning ensures maximum safety

Ensure your car is parked on flat, stable ground and the parking brake is fully engaged

Open the hood and locate the coolant reservoir and radiator cap

Most modern vehicles have a translucent plastic reservoir with high and low markings

Do not remove the radiator cap unless you are certain the engine is cold

If you're unsure, wait longer

Use a pan large enough to hold at least 10–15 liters to avoid overflow

Even small leaks can attract animals and cause fatal poisoning

Look for the radiator drain valve, اتوسرویس داوود usually at the bottom corner of the radiator

The drain mechanism varies by make and model—it could be a twist-style valve or a threaded bolt

Turn the valve or bolt gently to avoid stripping or breaking

Let the fluid flow until it stops dripping—this may take several minutes

Certain engines have an additional drain plug on the cylinder block to remove residual coolant

Use this time to examine all coolant hoses and their securing clamps

Even minor cracks can lead to sudden leaks under pressure

Install new hoses or clamps immediately if any show signs of wear

The cap’s seal and spring mechanism must be intact to preserve system pressure

Once the old coolant is fully drained, close the drain valve securely

Now it's time to flush the system

This circulates water through the entire cooling circuit, including the heater core

The flowing water dislodges sludge, rust, and debris trapped in passages

Never drain hot water—it’s dangerous and can warp components

Open the same valve and let the water flow into the pan

Repeat this step if the water comes out dirty

Using the wrong type can cause corrosion or gelling

Always use the type recommended by your vehicle’s manufacturer

Most modern vehicles require a 50 50 mixture of coolant and distilled water

Choose pre-diluted coolant if you want to avoid mixing errors

Do not exceed the max level—coolant expands when hot

Overfilling can cause pressure buildup and lead to leaks or reservoir rupture

Start the engine and let it run with the radiator cap off

This is normal and expected during the bleeding process

Keep the engine running until bubbles stop appearing

Add more coolant as the level drops

Allowing full cooling prevents pressure-related spills

Tighten the cap until it clicks or locks into place

Coolant contracts when cool, so level may drop

Add more 50

Run the engine for 5–10 minutes and visually inspect all connections

A functioning heater core indicates the system is fully bled and circulating correctly

Dispose of the old coolant properly

Many retailers offer free coolant recycling—call ahead to confirm

Never pour it down the drain or on the ground

Consistent coolant service prevents costly repairs and keeps your vehicle running smoothly

Mastering coolant replacement empowers you to maintain your car’s health with confidence