I assume if you are flushing the system and doing general repairs and upgrades, that you will be replacing the expansion valve (you should do this). Do not throw the old one away....secure it in a vise and use an electric drill with a 1/4 or 3/8 inch bit and drill out the insides of each side. Then blow out all the chips. Now re-install this in its normal place, and you will now be able to flush the evap. from the engine compartment using the ends of the two hoses, and you will clean the hoses as well. Also, this method makes it easy to forward and reverse flush.

Good Luck,

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)