Rick's Free Auto Repair Advice

Coolant flush – Should you replace coolant?

When and how to get the right coolant flush service

Many shops advertise coolant flush services and they often issue discount coupons. You may think you’re getting a proper coolant flush when you’re really just getting a radiator drain and fill. Here’s an example of a radiator flush coupon offered by a chain operated repair center. They’re not deceiving you–you’ll get a radiator flush.  It’s just that you don’t want a radiator flush, you want a cooling system flush. There’s a huge difference between the two and the drain and fill can cost you big time down the road in terms of cooling system failures and expensive repairs.

Why do you need a coolant flush?

Engine coolant does more than just prevent freezing. It contains anti-corrosive additives that protect your radiator, heater core, water pump, and heater tubing from deteriorating. See this post for more information. Once those additives are depleted, corrosion starts to eat away at all those components from the inside-out. By the time you notice the failure, you’ve done significant damage to the entire cooling system. Here are some examples of the types of damage from worn out coolant:

Worn coolant corrodes water pumps

corroded water pump







Worn coolant corrodes the radiator

which antifreeze







Worn coolant corrodes the heater core

clogged heater core







What’s the difference between radiator service and a full cooling system flush?

When a shop advertises “radiator service,” they’re simply offering to drain the coolant from the radiator and refill it with new coolant. Shops usually post discount coupons for this service at $49.99. The radiator only holds about 1/3 of the coolant in your vehicle. So you get a false sense of security because the shop hasn’t actually removed the other 2/3rds of the exhausted coolant. A radiator service is a complete waste of money and a rip-off.

Then there’s “cooling system service” which might lead you to believe they’re flushing the entire cooling system and replacing the old coolant with new coolant. Maybe, but some shops simply pull the lower radiator hose from the radiator and drain the radiator and the lower portion of the engine. That still leaves old coolant in the heater hoses and the heater core. This service usually runs about $99 and it’s another rip-off.

A coolant flush is what you want. The shop uses a special flushing machine that pulses clean water  throughout the entire engine, radiator, heater hoses, and heater core. Then they add new coolant and bleed out any trapped air. Because this service takes longer and requires more new coolant, the cost is around $180. But it’s the ONLY way to remove all the old coolant and fully protect against corrosion.

What’s the right coolant?

Every car maker specifies a different type of coolant for their vehicles and the coolant is engine specific. The chemistry is designed to work with the metals and rubber seals used in that particular engine. Using the right factory coolant is a huge correct coolantproblem for independent shops because they can’t possibly stock all the  different types. So many shops use a “universal” coolant. Unfortunately, not a single car maker approves of these universal coolants. If you’re going to use an independent shop to do the work, demand they use the factory coolant. Factory coolant costs more than universal coolant. But it’s only a difference of about $10/gallon and most vehicles require only two gallons. For that small difference in price, you should demand the right coolant.

How often do I need a cooling system flush?
Most car makers list a recommended coolant change interval in the owner’s maintenance guide. If you’re not sure if you need a cooling system flush, ask the shop to test your coolant. There are several tests they can perform:

Test for freeze protection using a refractometer

how to test antifreeze, coolant






Test for alkalinity using test strips

coolant test strips






Test for anti-corrosion additive wear using a meter

antifreeze electroylsis

If your coolant fails any of those tests, you should authorize a complete cooling system flush.

©, 2016 Rick Muscoplat


Posted on by Rick Muscoplat

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