Oil in water

[northyorkspaul]

Sorry if this is going over old ground....my 406 99 2.0 hdi with 211,000 miles as just put most of the oil into the water.Does not appear to be water in whats left of the oil in the sump.Never overheated and still runs fine now, oil light goes out,sounds just the same as ever.....it as a oil cooler and I have seen on this forum that someone had same prob and said it was the cooler,does anyone know if this could be the cause?....and how do you tell?....thanks.