Hi everybody. I've got a boiling coolant issue with my C180. I changed my head gasket last year november. The car has been good till now. At the speeds of 110 - 150 km/h, my coolant boils over and spills away. I changed the viscous coupling almost a month ago. But I've realised that at high temperatures the viscous coupling doesn't kick in. I may be wrong though. Please I need some advise.