I think he is saying that the rear suspension was disconnected (isolated?) from the hydraulic pump and just filled with an oil so that it would act somewhat like a regular shock abbsorber. Maybe because of a problem with the pump?

Either way, if the rear end is not overly bouncy or a harsh ride, I would leave it as is until problems start to arise. By then, though, you might have to replace the rear cylinders (shocks) with new ones and get the pump working. Unless there's a way to get a regular shock absorber to fit in there.

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now