Danni68

Hi We have a 2006 grand voyager 2.8crd that will happily sit in traffic in hot weather but once you drive over 60mph the temp goes up quickly and you have to have the heat on and slow down to stop it overheating. It has had a new water pump and timing belt, new coolant tank cap and we have flushed the system a couple of time but still it does it. Any ideas why this happens?? Thanks in advance