Ok i was driving yesterday and i noticed a rapid clicking noise coming from the engine when i tried to accelerate. I dropped down a gear and tried accelerating again and the same noise. So i pulled over and pulled up the bonnet, and it was steaming. I waited for about half an hour and put some coolant in had steam from the radiator overflow hole, and coolant didnt seem to be filling the header tank as much as it should. The temp did go down in the end, but after i was towed and the temp was right down i tried starting the engine, but it seemed like it was trying to start but did not. Some people have said i may need a compression test. Firstly what is a compression test and would that be the way to go?? Any help appreciated guys.