My C240 warms up on cold days (10 degrees) after 15 or so minutes of driving. I suspected a faulty thermostat, so I replaced (used Wahler 87 degreee unit purchased from MB dealer) and noticed no changes in slow warmup. The car is manual transmission and I usually coast when going downhill. I also don't idle when first start the car and immediately drive it.
What seems to be causing the slow warmup??

I wouldn't be too concerned. The slow warm-up is most likely due to the low ambient temperature. If there was a problem you'd get a Check Engine light, with fault code P0128/P202C. If the engine coolant temp is below 75C, but the engine management system thinks it should have risen to at least 86C, the fault code will be stored. If this happens on two consecutive "trips", the CEL will illuminate.

ILUVMILS, I'm struggling with your response--I have the exact same car with the exact same manual transmission, exact same issue--75K miles, original stat to my knowledge-No check engine light-(203.061/112.912)

Same very slow warm up-

By comparison, my 104 powered 124 has 40°+ in less than a mile really no matter the outside temp, which after having done the head, I realized the cooling jacket on the 104 is very tight. Additionally, my normally aspirated 606 powered 124 warms up faster than this C240?

So, is the 112 a cold hearted beast or is there really something else going on here?

Best,
G

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