New tstat just broke? Maybe?
 

I just replaced the thermostat on my 190E about 3 months ago, and am wondering if they are so fragile to break like this?

my temps used to run at 80C or less, until i replaced the tstat with a new one and then it ran around 87C under normal driving conditions.

today, I ended up idling in traffic for around 30 mins, and it was hot day, so the temps were consistently near the 100C mark. i parked the car finally to get some dinner, and on the drive back home, I noticed that my temps were back to the 80C mark again, and sometimes even lower. Now i suspect that the tstat is stuck open again.

are these thermostats so susceptible to being stuck open like this just from exposure to high temperatures?

I bought an off brand thermostat. Turns out that the seal supplied with this was not good.
Wouldn't let the thermostat sit properly. Worked fine for a month or two and then lost its stiffness and failed to do it's job.
Try a new genuine seal first - they are cheap. (That is if you don't have the correct OEM one).

I got a Stant 'stat for my 190E. No problems noted. The old stat was stuck open about a 16th of an inch.

Behr make the best stat for Benz...and I agree about the seal..it must seat nicely or it will distort the flange base of the stat., affecting open/close mechanics .....very important.

I'm using a behr one that I bought from **********.