Originally Posted by Clavurion

I've washed M57 many times. First remove engine cover and put some plastic to cover the alternator. Spray degreaser (on cover separately) and let soak. If possible use some brush on surfaces. Pressure wash (preferably with warm water) from some distance avoiding long term spray on electrics. Remove plastic you installed to cover alternator. Start engine to warm it up. Use compressed air to dry excess water. Install the engine cover on the next day so the top of the engine (and bottom side of the cover) can first properly dry out.