Coolant is very much needed in your car and without it the engine will very quickly overheat often causing irreversible damage. You may not realise that you have a coolant leak until a warning light comes up on your dash, you notice a puddle on the floor under your car or your car goes in for repair work or an MOT and it is picked up there. Another tell tale sign that your coolant is running low is your temperature gauge shotting up and down. You may also notice that your heaters in the car begin to blow hot then cold air, this can be a warning to top up your coolant. Occasionally coolant will need to be topped up anyway but if you are having to do it every couple of months then the chances are you have a small leak. If the leak is only small then using a product such as Radweld may help repair the leak but if the hole is large then you will need to find out where it is coming from and replace or repair the defective part. IF you are not sure where the leak is you can get a special dye that you put in your coolant system which will then show you where the leak is coming from.