My 1988 560SEL is overheating. I have combed the past post trying to nail down the problem. Still no answer.

One day while driving for about 15 minutes the temp maxed out and the coolant poured from the over flow. I ran a test on the fan clutch and it failed. So, I put in a new one and it passed. However, it still breaks 120 in about 15 minutes; I pulled the temp sender to fill the engine back with water to insure there were no air pockets. Still it hit 120. I ran the inside heat and it works great especially at 120 engine temp. I checked the thermostat and could not find one. Maybe the previous owner removed it? I assumed it was in the housing that the temp sensor is screwed into??? All my secondary fans are working. When I drive the car it has plenty of power. Just before it reaches 120 I bring it back in to cool down.

What in the world is going on? Is it finally over between us?

Your comments are appreciated.