If you have a bit of DIY inside you refer back to some recent threads here about changing out the water pump. Look in the DIY section and there is a thread on changing the water pump on a M103.

Either the bearing has gone inside your waterpump and coolant is leaking out the outlet hole or the O ring between the pump and engine has failed. Either way it's quite a job to change the pump.

Hit the buy parts icon at the top and start on your way.