How much can I save by changing my coolant?

Coolant £2-£9 per litre

Coolant change: how much does it cost?

Ready-mixed anti-freeze won't break the bank, especially when bought in five-litre bottles, which brings the price per litre down. It's the labour involved that makes up the bulk of the bill if you get this job done by a garage.

Most mechanics should be able to complete the task of draining, flushing and refilling in around an hour, which is why you'll save yourself around £150 by changing your car's coolant yourself, with help from Haynes.

Find a manual for your car here and start saving with Haynes

How coolant works in an engine

Coolant added to an expansion tank

Coolant is your engine’s lifeblood. The fluid keeps the motor at the correct operating temperature, helping it to warm up quickly in cold weather and not get too hot when under stress – and when mixed with the correct antifreeze it prevents damage in cold weather and stops corrosion (so always add it).

Your car's coolant system consists of an expansion tank, a radiator, a water pump, a thermostat and a series of pipes that connect all of these components to each other and the engine block; the coolant runs through channels within the block to help transfer heat away from the engine and keep it at peak operating temperature.

How long does coolant last?

Coolant is deeply important for car cooling, and makes sure the engine is at the right operating temperature. It’s the liquid tasked with coursing through your engine to keep it cool and corrosion-free. It also works its way through the heater matrix to keep the cabin warm.

Take a look at your car’s handbook for coolant change intervals. Some older models – including classics – need a coolant change every two years. They require what's known as Inorganic Acid Technology coolant, which is kinder to the seals and gaskets used on older engines. It's typically blue in colour but is becoming harder to find in shops. Don't be tempted to swap it for longer-lasting 'Organic' coolant (see below), because it's likely to damage your classic's seals.

Modern vehicles can go for 10-15 years or even more with the fluid they come out of the factory with – you may see 'lifetime coolant' referred to, which is often (but not always) pink in colour. This coolant is also known as Organic Acid Technology. Once you change this 'factory fitted' coolant for aftermarket coolant, we'd recommend renewing it every five years, unless the instructions on the bottle say otherwise.

Whichever coolant your car needs, we'd recommend checking its strength each autumn, and certainly before cold weather arrives, to make sure it's still at sufficient strength to protect your vehicle from a deep freeze.

However, if you're changing a part that's connected to the cooling system, such as the water pump, you'll need to replenish some or all of the coolant well before these intervals.

Can I use water instead of antifreeze?

Coolant poured into the expansion tank

You should never just put water in your car cooling system. Water on its own will do nothing to prevent corrosion. Your engine needs coolant with antifreeze mixed in, which is chemically balanced to react in certain ways under certain conditions.

In winter, the additives in coolant prevent it from freezing. Use plain old water and it'll freeze in your engine block. Water expands when it freezes, which will crack the block. That's very bad news indeed.

Those additives also raise the coolant's boiling point, to prevent the engine from overheating, particularly when it's working harder.

Coolant change: when to do it?

“If you can’t remember the last time the coolant was changed, do it now”

If you're planning on changing the coolant as part of a car's servicing procedure, always consult your vehicle’s handbook for recommended intervals. If you can’t find evidence that the coolant was changed when it should have been – and especially if it’s looking cloudy and discoloured, change it now. Part of the cooling system service involves flushing.

Always wait until the coolant is cold before draining it. Don’t allow antifreeze to come in contact with your skin or painted surfaces of the vehicle and rinse off spills immediately with plenty of water. Never leave antifreeze lying around in an open container or in puddles on the floor; children and pets are attracted by its sweet smell and may drink it.

Check with local authorities about disposing of used antifreeze. Many communities have collection centres that will dispose of antifreeze safely. Never dump used antifreeze on the ground or pour it into drains.

All cars are slightly different, so if it is time to change your coolant, find your car for specific instructions.

How to renew your coolant

Here's an example of how it’s done

A very brief summary of the task:

  1. Make sure the engine is cold and raise the front of the vehicle on axle stands. You may need to remove the under-engine cover
  2. Place a container under the radiator and undo the drain valve
  3. Remove any other drain plugs as instructed by Haynes. Flush the system as many times as necessary
  4. Refill the system with the correct antifreeze, following Haynes’ instructions for bleeding/topping-up procedures

Why you should change your coolant

Draining, flushing and refilling the coolant will help prevent formation of rust and corrosion, which can impair the performance of the car cooling system and cause engine damage.

Over time the antifreeze chemicals in the coolant lose their effectiveness, especially if you have to top up the coolant with water regularly. In harsh winter weather this can lead to the coolant freezing and expanding, which can damage components.

Tools you will need to change your coolant

Only basic tools are required for this job, although you may need to raise the car to remove the undershield.

  • Pan or bucket to collect water
  • Trolley jack (if necessary). Not your car’s emergency jack
  • Axle stands
  • Ratchet and socket set
  • Flat-bladed/Phillips/torx screwdriver
  • Rags
  • Pliers

Parts you may need

  • Coolant
  • New hoses and clamps