The 86 560 has 2 pumps but both are mounted at the same place, just behind the rear axle toward the right side of the car. I believe I would replace the filter mounted at the same location as the pumps. If the noise continues unplug the pumps one at a time to see which is making the noise. The reason for replacing the filter first is because it may be the problem and probably needs it anyway.

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84 500 SEL (307,xxx miles)