Engine temp gauge dropping- 2010 2lt TDI

[taff68]

Hi all,
Just had my engine thermostat replaced via main dealer as my engine temp gauge on the dash was dropping whilst stationary, very slow moving traffic etc along with a ERG valve? following the car being put through the dealers diagnostic device.
The fault (engine gauge) after three days has started to drop again whilst in slow traffic, anybody have any ideas what could be causing this fault as it seems the thermostat was not faulty?
What does the ERG valve do?
If i leave the thermostat as is,will it cause any damage to the engine.
Can i return the car to the main dealer as they have not cured the fault despite the diagnostic check and get them to investigate further free of charge?
Cheers.

 

[KrisKrk]

You SHOULD return the car to the dealer. They simply charged you for something that has not been resolved. If you have explained them what are the symptoms of the fault and they discovered it may be or it is the thermostat, they need to rectify it for you.

Was it all recently, in the space of days or some time ago?

I had the same problem during the winter time. Temperature was low, engine was gaining the temperature slowly. As I have 7 miles to work, It was taking good 5 miles to reach 90deg. If I would drive with heating on from the start, temperature would be nowhere near 60-70deg even after whole journey. NOrmal weather condition it would. If I reached 90 after nearly the whole journey and switch the heating on , temperature would've stay ok and heating would be efficient. If drove and switched the heating on before reaching 90, I had same issue as yours.

What I have read around is, that is a very common issue for vag vehicles during cold weather.
Heater control opens up the thermostat and coolant flow although engine hasn't reached 90deg yet, from what I have understood.

I had stat replaced in February last year and it was ok (not fine) for a month or so. Then, Spring came and I had a coolant leak from o ring. Got that replaced in the Summer, with new coolant poured in and stat replaced again and the issue came back this past winter.

Unless you're not loosing coolant and it doesn't splatter around the engine bay (like my A4 I had did, that turned out to be blown head gasket) you've got nothing to worry about.
Don't tell stealership about it as they will not inspect the car. Force them that, they didn't solve the issue that you've paid for and you want it done.