Overheating

I need some help with my current situation.

I have a 1989 300E with around 193,000 miles on it. I have recently run into a problem with the car overheating.

This is what happened the other day. I got in the car and started to drive it and within probably 5 miles the car started to increase in temperature. In an attempt to cool it down I turned on the heat in the car to blow hot air and all it did was blow cool air.

So, I immediately turned around and parked my car before the temp went up too high. When I did pull over and parked the car I noticed that there was antifreeze flowing out of my car from the radiator reserve tank out of the overflow hose.

I would greatly appreciate any insight into this problem.

Thank you
Ryan