I'm not sure of the suspension configuration on the 400SE, but on my 420SEL, the power steering fluid that would leak out, liked to drip over one of the subframe mounts. The rubber in the mount did not like this at all, and protested by swelling and making itself near useless. Unfortunately, the rubbers weren't replaceable, I had to get a whole new armature (not cheap).
So, not only did I pay to have the leak fixed, but also to have the subframe replaced, because I waited too long.
In essence: Check to make sure the fluid isn't leaking on expensive to replace parts.
"...rationality of thought imposes a limit on a person's concept of his relation to the cosmos." -Nash
04/71 280SE 195k
09 Jetta TDI