Liquid in vacum reservoir. Is that normal?

[juribe2]

Hi,

I removed the front right fender cover to get access to the coolant overflow tank (replace hose) and I discovered that there is some kind of liquid inside the vacum reservoir. About 1/3 of the tank is full with some kind of liquid stuff.

Is that normal? If so, what kind of liquid is that?

Car is a 1995 E320 Sedan. W124, M104.

Thanks