I have figured out why my collant was low, leaking LIM gasket, it's leaking into the injector pockets, at least it's not into the crankcase. I do already have all the gaskets to replace them but just have to find the time. I suggest you check around for water around the inkectors where they go inot the head to see if this is where your collant has gone, if that is what turns out out be your prob.