Many of posters have reported p/s noise and have replaced the reservoir and flushed the system to elimate the cavitation sounds you may be hearing. If your pump is making death rattle sounds then flushing and replacing the reservoir will reduce the noise level but not cure it. If the built in filter clogs up it will constrict the fluid flow and force the pump into working overtime until it fails. It is a quick replacement that only needs the clamps replaced if the hoses are in good shape.

As your system wears out there are only three issues to determine: rack, pump, line pressures. Only diagnostics will determine which is the issue and hence source of the problem. Any competent shop can determine this will a pressure gauge.
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2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green