How an engine’s cooling system works

Coolant system draining and refill image

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, even if you don’t live in a cold climate).

Take a look at your car’s handbook for coolant change intervals. Some models need a change every couple of years but some can go for longer.

This task is reasonably easy and requires only basic tools. It should take between 1-2 hours.

Every car is different, so before you view the full instructions, find yours…

When to change your coolant

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

Always consult your vehicle’s handbook for recommended intervals, but we think that two years is a suitable period. If you can’t remember the last time the coolant was changed, and it’s looking cloudy and discoloured, change it now. Part of the cooling system service involves flushing. If the coolant is changed on a regular basis you may need to flush only once before refilling.

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 which 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, use our before you begin checklist, and find your car for specific instructions.

How to change your coolant

This is a clip from a sample video. Find the full step-by-step task for your model

A very brief summary of the task:

  1. Make sure the engine is cold and raise the front of the vehicle on jackstands. You may need to remove the underbody shield
  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

Periodically, the cooling system should be drained, flushed and refilled to replenish the antifreeze mixture and prevent formation of rust and corrosion, which can impair the performance of the cooling system and cause engine damage.

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

Before you begin

Tools you will need

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
  • Floor 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

Every car is different, so before you view the full instructions, find yours…