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More than likely you need a new thermostat. In the old days they failed closed which overheated the car. Now they fail open, which is much better and the result is exactly what you are describing.
As mentioned above thermostat. Im just surprised it didn't throw a code yet.
mine threw a code twice for thermostat and temps drop on eway guessi just need thermostat only ? Sorry to revive old thread didn’t wanna start a new one . 14ml63
The cars coolant temperature gauge stays at 80•c when driving local when driving normal.
When you drive on the motorway, the temperature drops to 65-70•c.
You can get the temperature to go around 90•c if you drive the car hard. The heaters do work but when the temperature drops, they go from hot to warm.
So to keep the car at 90•c I have to keep driving the car hard all the time. What could the issue be?
I have attached a picture of the car’s temperature after being driven on motorway for 45 minutes constant.
Thanks
Apologize for re-viving an old thread. I have a 15 ML and recently during cold weather I've been noticing the temp gauge stays stuck at 40 degrees for a solid 10-15 minutes after starting the car. After 15 minutes the temperatures slowly creep up to around 70. The thing I don't understand is that the outside temperatures are around 30-45 degrees Fahrenheit when this occurs so in some cases a running engine which produces a bunch of heat is somehow at a lower temperature than the outside air after 10 minutes? I got my thermostat replaced by the dealer a couple months ago when the cooling system failed, so it shouldn't be a thermostat issue, unless the OEM one is a faulty one. I also re-pumped the freon and the A/C blows ice cold. Compared to 10 years ago, the cars heat definitely is not as strong upon start-up and initial drive. Any suggestions?
Apologize for re-viving an old thread. I have a 15 ML and recently during cold weather I've been noticing the temp gauge stays stuck at 40 degrees for a solid 10-15 minutes after starting the car. After 15 minutes the temperatures slowly creep up to around 70. The thing I don't understand is that the outside temperatures are around 30-45 degrees Fahrenheit when this occurs so in some cases a running engine which produces a bunch of heat is somehow at a lower temperature than the outside air after 10 minutes? I got my thermostat replaced by the dealer a couple months ago when the cooling system failed, so it shouldn't be a thermostat issue, unless the OEM one is a faulty one. I also re-pumped the freon and the A/C blows ice cold. Compared to 10 years ago, the cars heat definitely is not as strong upon start-up and initial drive. Any suggestions?
I think you're confusing two measurements of temperature. The analog gauge on the dash is showing temperature in Celsius and it sounds like you are referring to ambient temperature in Fahrenheit. So if your gauge says the coolant is 40C, that's 104F - which is much warmer than the ambient air. I just replaced my thermostat and my coolant is now running around 190F (88C - slightly above the midpoint of the gauge) when driving the car.
If your interior heat is not getting hot, it sounds to me like you have an air pocket in your cooling system, which is preventing full circulation of coolant into your heater core. alternatively, the thermostat could be stuck in the open position. since you were just at the dealer for cooling system service, why not take it back and have them investigate? the repair should still be under warranty.
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