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Discussion Starter · #1 ·
Location NY, USA
2015 Mercedes GLA 250 4MATIC
39.000 Miles

Hi guys last night after driving for like 15 mins all of the sudden the engine heat goes to the maximum and I get the message that coolant is too hot stop vehicle, as I stop on the side of the road I turn off the engine go check the hood the engine seems perfect not any smoke just the fan working at maximum. I keep checking for like 5 mins for anything like smoke or leaks but everything is normal, I go back to the car turn the ignition on now the temp is a little higher than 80C (where it usually is) now I'm confused cause I dont think it lost around 50C on just 5 min usually you gotta leave it at least 30 mins to cool down, so I start the car and just wait on the side of the street for good 10 minutes and engine temp doesnt move at all keeps steady on normal. I start driving the heat is perfect I also gave drove little higher RPMs to check if its going to heat but nothing engine heat kept staying on level. After that I came home parked checked the coolant level was good. Today I got out again with the car same thing after 10-15 mins coolant too hot, this time I couldnt stop anywhere since I was on highway there were no shoulders. I kept driving with fear that my engine will blow at any moment but after 1-2 mins the temp just goes right back to normal. Im really confused if the thermostat has a problem or the water pump ?
Sorry for the long rant but Im just scared af lol.
 

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Since the coolant temperature has returned to normal under use I would think the pump is ok, or at least works some of the time. A faulty thermostat is the more likely cause. Thermostats, being ever immersed in universal solvent water, are highly prone to failure on most any vehicle. Fortunately they're relatively inexpensive.
 

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Discussion Starter · #5 ·
Since the coolant temperature has returned to normal under use I would think the pump is ok, or at least works some of the time. A faulty thermostat is the more likely cause. Thermostats, being ever immersed in universal solvent water, are highly prone to failure on most any vehicle. Fortunately they're relatively inexpensive.
I will take the car out today again and will update you guys again since I have no idea whats going on. Thank you for your replies and happy holidays!
 

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I will take the car out today again and will update you guys again since I have no idea whats going on. Thank you for your replies and happy holidays!
I have same issue on my GLA too, even a week after changing a new thermostat from dealer. Did you finally find out the reason, and did you get repair? Thanks.
 

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Discussion Starter · #7 ·
I have same issue on my GLA too, even a week after changing a new thermostat from dealer. Did you finally find out the reason, and did you get repair? Thanks.
Sorry I already sold the car. I took it to the mechanic back then and he said water pump might be stuck closed sometimes. I changed the water pump but it still happened one more time, after that it was ok until I sold it. I suggest washing the radiator with a pressure washer. maybe it has a lot of debris then you can start with water pump!
 

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Discussion Starter · #8 ·
Sorry I already sold the car. I took it to the mechanic back then and he said water pump might be stuck closed sometimes. I changed the water pump but it still happened one more time, after that it was ok until I sold it. I suggest washing the radiator with a pressure washer. maybe it has a lot of debris then you can start with water pump!
Just FYI theres some people who mentioned that the water pumps on the GLA's are known to have problems since they are new design.
 
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