I saw that small hose connects to radiator from reservoir, it can easily be removed, but I think releasing the radiator petcock would remove more old coolant from engine, and I am thinking using garden hose to force water into the engine through reservoir to flush out old coolant in the engine too.

Do anybody know where is the radiator petcock/plug is located ? what tool do I need to release that petcock ?

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'00 E430 Brilliant Silver/Ash