We need to understand more about where its leaking from.
On the M104 engine there are two classic leak spots, the first and cheapest is from the front left hand side above the alternator. This is normally the front timing cover gasket which is notorious for leaking and is difficult to get a good seal on. I had mine replaced for £70 although it still weeped slightly.
If its the head, they normally go at the rear left hand side. To check if it your head gasket, do the usual checks for oil in the expansion tank etc and then get somebody to start the car (from cold) whilst you stand in front of the engine bay. Within 30 seconds of the car starting if the top radiator hose on the right hand side of the radiator gets full of pressure, you have a head gasket problem....ie the exhaust gases are escaping into the coolant, hence the reason why the top hose pressures up.....this should normally be squiggy until the car is hot and the thermostat opens.
Head gaskets are not cheap to replace and can run from @ £400 upto @ £800, as most people take the opportunity to have valve stem seals etc replaced and the head may need a skim.
Thankfully the replacement head gaskets have a slight re-design which stops them from blowing so quickly next time.......ie; many head gaskets on the M104 engines can blow from @ 110,000 miles +
Whats the mileage on yours?
