Radiator Flush Cost (and How to Flush a Radiator at Home)

Is your radiator in need of a flush? Allowing the wrong fluids and deposits to build up can lead to overheating and damage. Flushing your radiator periodically is an important maintenance task that will extend its life.

This article provides a step-by-step guide to safely flushing your radiator at home, along with the costs involved of doing a DIY flush vs taking your car in to be serviced by a professional.

radiator flush cost

See Also: Transmission Fluid Flush vs Change (Which Do You Need?)

Radiator Flush Cost (DIY vs Professional)

Doing a radiator flush on your own will cost your relatively little as you’re really only paying for coolant and distilled water (and optionally, a cooling system cleaner). Expect to pay in the vicinity of $25 to $60 for a DIY coolant flush. This is assuming you have basic equipment like a drain pan, funnel, wrench, or any other tool you may need. 

To have your coolant flushed as a professional service, expect to pay anywhere from $100 to $200 in most cases. The exact cost will usually depend on where you go (an independent mechanic will be cheaper than a dealership). Some less reputable shops might only charge between $50 and $100.

The amount of coolant your vehicle needs is the other main factor when determining the price of a radiator flush. Usually the engine size will dictate how much coolant you’ll need. It’ll likely be somewhere between 10 to 28 quarts with the average being around 16 quarts (4 gallons).

A small 4-cylinder commuter car will require a lot less coolant than an 8-cylinder truck or SUV. Even fully electric cars like Teslas require coolant. Once again, your owner’s manual will let you know the exact engine coolant capacity.

How to Perform a Coolant Flush at Home

Below is the general process of cleaning your car radiator by flushing out old coolant. If you notice that you’re losing coolant with no visible leaks, it may also be a good idea to replace your radiator cap as they can go bad over time.

#1 – Drain Coolant

Obviously, the old coolant needs to be drained from your radiator first. Your engine needs to be cooled down beforehand, so make sure you haven’t driven your car for at least 30 minutes prior to starting this process.

While it’s beneficial for your engine to be warm before changing your oil (since the warmer, thinner oil drains better), no such benefit exists for coolant. You will need to have some time of drain pan placed under the radiator so that it can catch the coolant.

Make sure it’s large enough to hold all the coolant (check your owner’s manual for your vehicle’s coolant capacity).

#2 – Add Cleaner (Optional)

Once the old coolant has been drained from the radiator, you will now add special radiator cleaner to the reservoir of the radiator. You can obtain this cleaning solution at any auto parts store whether local or online. Thermocure and Prestone AS105 are two of the best radiator flushes out there.

After the cleaner is added to the radiator, add distilled water to the reservoir as well. Start the vehicle’s engine and then set your heater to full. For the next 5 minutes, the cleaner and distilled water are going to clean out all the sediment, rust, and other particles from your cooling system. Turn off the engine and let it sit for 30 minutes.

#3 – Drain Again (If Using Cleaner)

When the cleaning process is finished, you will need to drain all the cleaning fluid and distilled water from your radiator. This will be a similar process like before where you place a pan underneath the radiator and catch the liquid as it drains from the reservoir.

You may notice the water looking a bit darker than it did when you first added it. That is okay because it is a sign that the radiator flush successfully cleaned the cooling system. Now just flush the cooling system with regular tap water to ensure the sediments are removed and then drain the tap water.

#4 – Add New Coolant


Finally, you can go ahead and add the new coolant to the radiator reservoir. You will typically mix coolant/antifreeze and distilled water at a 1:1 ratio. So for every 1 gallon of coolant, you’ll want to add 1 gallon of distilled water. Check your owner’s manual just to clarify the exact amounts.

Although you can purchase pre-mixed coolant, you’ll get the most bang for your buck by purchasing the concentrated coolant and distilled water separately. Once you’ve added the correct amount of coolant (again, check your owner’s manual), start your vehicle and let the coolant run through your engine for about 15 minutes.

See Also: Symptoms of a Clogged Radiator

When to Flush Your Radiator

losing coolant but no leaks

Car manufacturers may give you different advice on when the right time to flush your radiator is. In general, you’ll want to flush it every 5 years or 100,000 miles, whichever one comes first. Sometimes you might need to perform it sooner, depending on what your driving habits are.

If you ask most auto mechanics, they’ll probably recommend you flush the coolant every 30,000 miles. But in most cases, that short of a flush interval is unnecessary. The best thing to do is dig the vehicle manual out of your glove box and see what the manufacturer recommends.

If you’ve had a major issue like a blown head gasket or cracked cylinder head, oil has likely made its way into your cooling system. Once the issue is resolved, a coolant flush is also necessary.

Mark Stevens

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