oil in water chamber

hello i have a 05 kangoo van 1.5 dci turbo oil is in the water chamber i have fitted a second hand oil cooler but the problem is still happening so i put a hose pipe on the bottom pipe of the chamber and started the engine when i looked in the top of the chamber it was running water then oil water oil and so on the van does not over heat no power lose no white smoke i only noticed it when i can to put anti freeze in so i do not know how long its been like this as like many as long as it starts its ok thanks for your replies