There are some strategically located flushing valves located throughout the system, one is at the lower right (passenger) side of the radiator, the other below the exhaust manifold, and the vent above the thermostat. I would imagine that with the radiator removed and a garden hose you could do a really nice job of flushing out the block, head, and water pump. After that, install the radiator and plain water. Warm up the system, turn on the heat, and then empty the system. I wouldn't run it with plain water for long since it can damage the water pump due to lack of lubrication. I am always very hesitant to load up the cooling system with a flushing chemical, since I think the only thing it is likely to do is deterioriate the fragile head gasket. (and it's not wise to let it flow all over the driveway).

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89 300te 222,222
92 300e 190,000