Its hard to say an exact amount. Renault say 0.5 litres but you'll waste a lot pumping it out until the bubbles stop and youll waste a little while changing the lines, when I did mine I used about 1 litre. For best results do it in this order: left rear, right rear. left front, right front. Make sure you keep the resorvoir topped up and never let it get empty so it sucks air in.