mawi88

Hi everyone,


I am new to this forum and I am disparate for help.


My Mercedes C180 2012 (petrol) is experiencing some weird engine temperature fluctuation. When the AC / heater is off the temperature is stable and everything is fine, However, when I turn the AC/heater on and drive on a motorway, the engine temperature starts to fluctuate rapidly ! it start jumping off between 120C degrees and back to 80C and I could hear the engine fan going on full blow ! As soon as i switch off the AC/heater everything goes back to normal and stable. My friend helped me capture a video of this happening, please see the link https://www.dropbox.com/s/sa4s3hi9by...itled.mp4?dl=0 (see minute 0:22).


Please note that i am not losing any coolant and no signs of head gasket damage. My car has only 34,000 miles on the clock and has been service all the time by Mercedes.


I took it Mercedes dealer to do a diagnosis and they kept looking for almost two days and they couldn't be sure why this is happening....they had a number of theories but nothing conclusive.


I changed the thermostat (along with the temperature sensor) and also change the Change Over valve (vacuum valve) but still the is issue is not resolved.


Now they are suggesting to replace the water pump and the engine belt (since it is making some noise)......


Anyone has a different view on this matter ?



PLZZZ Help

MJ50

moved to W204 forum...

meazz1

I had similar issue but the temp was not going to 120 and back to 80. It was dropping to 45 or 50 and back to 90.

I had seen this only after driving the car for the first time in a cold day. I never lost coolant or anything. I replaced t-stat and coolant the issue seems to be improved but did not go away completly.

Once the car is driven for a while it never happened.

I moved on and stopped loosing sleep over it.