Water pump maybe?
The low water level came on in my 86 560 sl the other day, I checked the electrical connection, added a little coolant, light went out-end of problem. A couple of days later, the light came back on, I noticed some fluid on the garage floor, smells burned.
It cools perfectly, never overheats.
I got up under the car and saw no fluid anywhere on the hoses but a little on the middle of the subframe. I am guessing maybe it is coming out of the overflow from the radiator but would like to be sure.
Since it it cools fine, I am not real suspicious of the waterpump but would like to know how to troubleshoot to find out. No strange noises to speak of.