Fan clutches can be a pain. Keep in mind that only Sachs is the OEM for the 119 series. Yes, they are $400 even from the cheapest sources. After checking around I finally just bought one from Phil on this site.

I tried 3-4 Chinese brands (remarketed by Behr etc), and although they fit, operationally they are a mess. These cheap fans are made to fit thousands of motors, from automotive to generators to tractors to backhoes. They have a preset off/on and they are built to behave quite differently than the Sachs. I saw where the Behr's will fit a 2004 Bobcat loader also. Same clutch.

The cheap fans basically are hard to stop. They'll drag a big V8 with huge fan lockups, and your motor will make enough noise to wake the neighbors. Not to mention mileage/efficiency. Only under certain situations do these cheap fan clutches disengage. They are made for a steady-rpm type motor.

The cheapies will come on and stay on until the air moving over the radiator is near 170deg F. Then they'll turn off for 2-3 minutes, then back on when air gets to the 190deg F level. And stay on. They are NOT made for Mercedes Benz, although the physically and mechanically fit.

Now the Sachs (OEM) which are built specifically for MBs, will stay on for about 30 secs at engine start. The fluid moves around and the fan will quit/disengage. As the air temp gets warmer, the Sachs will GRADUALLY engage - unlike the Bears that are either off/on 100%. So, around 185deg F the Sachs will find a good fan engagement, about 30% engaged, and keep the motor cool the way it was designed - WITHOUT a 100% lockup and ensuing issues.

A fully engaged fan running at 4k RPM is a danger and a disaster waiting to happen. I contacted Behr about this, and their only reply was "it fits many engine manufacturers".

So lesson learned from someone trying to be cheap - in this case save yourself the trouble and get the OEM.