Need some input regarding the accuracy of my coolant temperature gauge on my '14 E250 with 38K. The gauge moves up normally as the car heats up. After reaching operating temperature as indicated on the gauge (90c) the needle will fluctuate between 80 & 90 degrees. This fluctuation happens at both highway speed and city driving. No codes, overheating etc. The reason I ask, is that I have owned a number of MB's and once the gauge reached operating temp it never moved off the mark.

Any insight would be welcome.

Chas

 

I'd guess thermostat?

 

Cooling system is doing what it's suppose to be doing. I have OBDII software that I drive with and am able to monitor the Coolant and Oil Temperature of my '14, ML 350 Bluetec. I also see the coolant temperature fluctuate a lot between the high 90's and and high 80's depending on if I am sitting i traffic or cruising along the highway. Whereas the oil temperature fluctuates a lot less and if it does fluctuate, takes a lot longer to change.

 

Dash gauge is dummy gauge. Check the temperature with scanner before jumping into any conclusion.