Vauxhall vectra 2.5 v6 sri 'arctic' 98 model 88000 miles. hi, i got oil blowing into the coolant tank.. a new oil cooler has been fitted recently, before i noticed this. the car heated up bad on my last journey. i replaced the filler cap on the expansion tank, to notice a very alarming amount of oil, in what was left of the water. seems coolant system, is full of oil, so not 'cooling'.. turned off engine, at first sign of heat up.. hav'nt run since. need to flush coolant system, but whats causing this? is this gasket failure? oil level on 'dip', into sump, is ok, and no 'butter', on underside of 'oil fill cap.. please help.. thanks.