The block drain valve is on the RH side of the block under the rear exhaust manifold. It has a nipple that you can attach a drain hose to - about 3/8". Makes it very easy to change coolant without spilling a drop.

I can reach the valve to loosen it from the front side using a crescent wrench. The radiator drain valve is behind the removeable cover on the RH side of the valence panel. It also has a nipple to attach a drain hose.

If you want to flush the system with water, remove the heater inlet hose from the back LH e of the engine and flush both the engine and heater circuit. You can do this mess free by rigging up some adaptors to your garden hose.

Changing coolant on M103 engines is the easilest and least messy of any car I have ever owned,

Duke