Hello Doug,
Very cool that you found a '66 with sliding metal sunroof and 4 on the floor. Same as my car, and a fairly rare build combo.

Look at the top of the differential area and see if there's a big horizontal metal cylinder or a spring. The metal cylinder is the Hydropneumatic Compensator. It's fluid filled, and pressurized, capable of leveling the car, as the car drives along. I'm guessing that's where your fluid is from. Usually though, when it goes bad, the rear of the car will drop, because the compensator no longer has enough pressure or fluid to pump itself up and support the weight of the car. People buy the spring kits to replace them, because the rebuild costs about a grand. You'll find used ones on ebay all day long for a few hundred bucks, and one of these could be sent away to be rebuilt, should you want to go that route. I still have one in my car, and really enjoy the ride, but that's just me. A guy on the BenzWorld forum for vintage MBZ, "suktinis" knows where to get the Compensators rebuilt, by the company that made them. Contact him if you want one rebuilt. Niemoller in Germany offers a rebuilding exchange service, but they are using the same company, and adding to the price.

Regarding the sunroof: The interior ceiling panel can be pulled down, from along the front edge, and then flexed in a bow, downward, and removed. This will give you access to the underside of the sunroof, and some of the pivoting internals. You can carefully lube them with Kroil and then TriFlow, but be careful not to get spray or dripping onto the headliner. You'll probably want to remove the sunroof motor completely from the car, take the covers off of it, and lube it up inside. They can get all rusted up and even seize. With the motor removed, and the sunroof cable free to spin, you might be able to manually move the roof. Maybe at that point you can get the roof slide rearward enough to clean and lube the track areas at the front, and then begin manually moving the roof back and forth, and upward into the closed position, repeatedly, and free up any of the pivots that might be stuck.

It looks like a nice car, but dear gawd, those fender mounted mirrors have got to go!

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