Exactly what did your friend put in as replacement fluid? ATF maybe? I hope it wasn't brake fluid! The answer to that will explain if its a chemical mistake.
Buy a bunch of cheap PS fluid, the OTC kind for generic cars, usually clear, pour it in as described while turning lock to lock and use a big jug to catch the old fluid. Repeat that until its clear then put in OE fluid the same way, you'll need 2 or 3 jugs of it.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!