I have a hydraulic leak above the cross member. Should I still drive it? on 1991 Mercedes-Benz 300TE 4MATIC

I don't want to burn up the pump. What should I unplug?
The guy I got the car from said he replaced an o-ring in a sending unit above the cross member and it stop[ped the leak for about a year. Any idea what part he is talking about? I want to order a new part, not another o-ring, before I jack up the car and remove the cross member.

Asked by for the 1991 Mercedes-Benz 300TE 4MATIC