You have to wrestle the box around a bit. If I remember correctly, you must pull it off the firewall, tip up a bit on the bottom and then rotate a bit CCW to "unhook" the expansion valve from the cutout. Fiddlesome but it does come right out.

Very awkward position, crouching there in the front seat footwell....

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!