Hi all,

I need your advice.

The car is 2011 B7 Passat 2.0 TDI(140) DSG and mileage is about 110k miles.

Few weeks ago, when the weather gets cold down to 0 degree, I noticed coolant temperature went down to 60 degree whilst cruising on A-Road or motor way. The gauge was solidly pointing 90 degree before this happens for more than one year since I got this car. I am a cabbie so the car has been used whole year constantly and there was no issue in the winter last year.

When the temperature gauge goes down, the hot air temperature also goes down correspondingly.

So I first doubted the thermostat and replaced with a genuine thermostat from TPS but no luck.

Then I replaced coolant temperature sensor on the engine, again with a genuine parts from TPS. When I take out the old sensor, it's anodised gold surface was peeled off. So it was an obvious issue on the sensor. Since replaced this sensor, I felt some improvement as the gauge stays on 90 most of the time but sometime still temperature goes down to 70 degree on cruising(even outside temperature is 9 degree...) but recovers to 90 soon after stuck in traffic. However, the weather has not get that cold since I replace the sensor, it may have not been improved.

Then I changed another coolant temperature sensor located on the hose, which I believe to deal with radiator fan. But no luck.

Can anyone have any thought on the cause of this issue and advise if anywhere else I need to check on it?

Thanks in advance.

kimken