[Jamesp]

There is a drain plug in the bottom. As i recall its an 8 or 10 mm allen screw. Looks like a little round metal button on the aluminum tube manifold under and in front of the engine. Using detergent will greatly increase the cleaning, but it can also foam. I'm not sure how that behaves in a water pump. You'll want to make sure there is no detergent left in the cooling system when you are done if you go that route. If you do use detergent please take photos and let us know how it goes.