Hi guys, i own a w204 c220 2008 and today i notices that my car got late to operating temperature, as you can see in the picture below, i drive for 36 minutes for temp to reach 90 c, is my thermostat broken? How can i check it out?
Thank you!

 

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No cel, coolant level is ok, no job done, once it hits 90c it doesnt move and works fine. When i checked my coolant i saw this gum like things what are those. Should i do a coolant flush?

 

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Quick update it was the thermostat stuck open slightly which caused the issue of engine taking longer to reach operating temperature.