Okay...so I've searched quite a bit on here and other forums but haven't found any definitive answers on how to identify common power steering problems before shotgunning over $1,000 worth of parts. The pump alone is $350+ for a rebuilt. Some of the hoses are $250+ EACH! I've flushed the fluid a few times but haven't replaced the canister with the filter in it yet or any of the lines. The fluid isn't leaking out because the canister is always full.

I saw on a certain parts site that there is a hose going to a "Power steering cooling coil". Is that the silver box on the lower front passenger side of the radiator that looks like a miniature window a/c unit with two hard lines attached? I can't seem to find any good power steering system diagrams anywhere.

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Current:
2001 BMW X5, 4.4i, 138K miles, Black & Tan.

Past:
1984 318i
1993 318i
1993 325i
2001 325i
1997 528i
1974 Porsche 911 2.7
1976 Porsche 911s
1978 Porsche 911 Targa
1985 Porsche 924
1987 Porsche 944 S2 Cabrio