i wonder if anyone can tell me what may cause this, i was giving my cossie a real hiding last night , when i raced a new bmw and an evo i left them both in my rear mirror according to my speedo it was 155 mph, when i slowed down i realised my engine was knocking, i creeped my car back home which wasn,t far on lifting the bonnet i realised the header tank was swollen and split on the weld all the water was gone and the car sounded like a london taxi, i will have to take the engine out tommorow and find out what damage has been done but wondered if anyone knew why it would pressurise like that cheers cosbag