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Draining and Refilling Coolant


Having the right level of coolant in your car engine is a lot more important than you might think. Coolant stops your car from getting too hot and overheating. That's why it's really important to make sure that your coolant levels are correct at regular intervals – make it part of your weekly vehicle checks and you can’t go far wrong.

​​​​​​​Ok, so what do I need to do?


High pressure and high temperatures can make it extremely dangerous to open the radiator when the engine is hot. With this in mind, always make sure that the car has been standing for around half an hour so that the temperature can cool down before you even think about checking your radiator and adding coolant.

Having opened up the bonnet and secured it, take a minute out to have a good look at your radiator. Check it over and make sure that there is no dust or debris covering the radiator top or sides and restricting the flow of air - this is one of the most common reasons that engines overheat! If there is any dust or debris, clean it off and make sure that the air flow is clear.

What am I Looking for?

  • Look at the coolant hoses and radiator and make sure that there are no tears, damage or leaks.
  • Looking into the coolant reservoir, you should see a see-through container through which you can see the fluid inside. There will usually be some kind of indicator on the cap that this is part of the cooling system.
  • Have a look at the coolant level in the reservoir. You should be able to clearly distinguish to the two levels marked 'low' and 'full'. Check that the coolant level is somewhere between the two, not too far in either direction.
  • If the coolant comes below the low mark, you will need to add more fluid.
  • Simply pour the coolant into the top of the reservoir. If there is no coolant in the reservoir you may have to pour some directly into the radiator. Your owner's manual will give you more guidance in this area in regards to the type of coolant to use and at what concentration – there are many different types so make sure you are using the right one for your vehicle.
  • If the level falls below the 'low' end after you've added fluid, it seems likely that you have a leak somewhere and you should get a professional mechanic to check it out as soon as you can.

If there is enough coolant in the reservoir, have a look at the colour. They tend to be brightly coloured fluids; green, red, yellow, blue - and usually thin and transparent. The coolant should be clean and free of debris. If you see something else in the coolant reservoir, such as oil, then you may have an engine defect somewhere that will need checking out by a professional.If it appears to be brown or a reddy-brown rusty colour, your vehicle may need a radiator flush. You can do this yourself but you should only attempt this if you are confident enough to do so as it is quite a complicated procedure. To drain the system, follow these steps:

  • Open the radiator drain valve and drain out the used coolant into a container or bucket that's big enough to hold it all. Once it's empty, shut the valve again.
  • Dispose of the coolant legally. It's a hazardous material so make sure you follow the laws for your area and don't just go pouring it into your nearest drain.
  • You should then flush out the radiator to clean the engine out. Use a cooling system flush (available from places like Halfords) to make sure that the inside of the system is clean and grease free before you refill with the new coolant. Fill the system up with clean water, replace the cap and run the engine for as long as the flush product suggests. Turn the car off and let the engine cool down. Follow step 1 to drain the system again, close the valve and fill up with clean water. Run the engine again, this time for around 15 minutes. Let it cool down and redrain the engine for a final time. Remember to dispose of the liquid the same way as the original coolant.
  • Check your owner's manual and add the coolant as required. Usually, water and coolant should be a 50/50 combination.
  • Once the coolant has been added, start the engine and allow the system to run with the heater on high. If the temperature light comes on or there is no warm air from the heater, you should call in a professional as something may have gone wrong.
  • Check the coolant level about a week after you filled it to make sure that the coolant and the water are mixing well. If it has dropped top it up again to 50%. check again a few days later and if the levels are low again, seek professional advice


Disclaimer: The information in the article is for general purpose information only and should not be constituted as legal advice. This article has been produced by a third party and Jardine Motors does not take any responsibility for the completeness, accuracy, or reliability with respect to the website or the information provided. Article last updated April 2018.