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Hello, I have a C300 w205 2015 Sedan with only 54k miles on it. I've had an issue with a spike in engine temperature for a while now without knowing why or what the issue is. By spiking I mean that normally, in the city, the engine temperature sits at around 85-90 Celsius (very normal for Florida heat), but ONLY when driving on the highway for an extended period of time, VERY RANDOMLY (it doesnt happen often) will jump all the way to the max engine temperature and the red box will light up in my engine temps. This only happens when I drive any speed over 60mph consistently and the engine has been on for ant least around 15 minutes consistently driving over 60mph.
However, this is where it's weird: when I let go of the gas pedal after consistently driving 60mph+ for a while, the engine temperature turns to red... but if I accelerate the car, the temps go down from 120 Celsius to 85-95 Celsius within a 10-second time frame. It has never stayed at 120 Celsius red for over 10 seconds. It has been borderline 115 Celsius and then it flicks into 120 territory and back rapidly. It's really odd and happens randomly, and semi-rarely.
Does anyone have any idea what this could be? I have never heard of an engine heating up and cooling down in less than 10 seconds going from 85 degrees to 120 degrees and back down to 95 degrees. If my engine had temperature issues, I'm sure the temps would stay at 120. Around 100 degrees (once it gets to this temperature, I know the car is gonna start going to 120 soon) Less than 3 seconds after the previous picture 2 seconds after 1 second after Immediately after Again, immediately after. Flickering between the red and borderline red.
Update for anyone with the same issue:
Took it to a mechanic friend of mine, first replaced thermostat but it did not fix the issue. After replacing the water pump, my car runs better than ever, absolutely 0 temperature issues.
Water pump was the cause of the issue, but I'm glad the thermostat was replaced as we noticed the plastic tips were starting to deteriorate and would likely cause a problem in the future if it hadn't been fixed.
Glad you got this fixed. I was also thinking it was your water pump. Since the Benz has a mechanical plugged in thermostat an error would be coded as a thermostat related issue but there is no way to see there water pump, so my guess since you didn't mention a check engine and code.. the thermostat was not the problem.
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