A3 1.8 2013 TFSI Temperature Gauge issue

[WhySoSerious]

Little issue with my temperature gauge. Shoots up to 90 degrees C within 10-15 minutes. Then goes back down to one bar on the gauge 50/60C. Pretty much stays there for the whole journey (Up to an hour). Got an engine warning light, plugged in VCDS and got:

P0116 - Engine Coolant Temp Sensor (G62)
P2181 - Performance malfunction in Cooling system.
Stuck open thermostat? Changed the G62 Coolant temp sensor. Still doing the same.
Thing is with this A3 - 2013 S-Line 1.8 Petrol the thermostat is location in the water pump assembly. I’m under the impression along with my mechanic the whole front of the car needs to come off for access. And if it’s coming off I may aswell change the water pump too along with the stat.
If anyone’s had similar experiences let me know. Expensive job it’s looking like sadly, I’m pretty locked onto the idea of the stat being stuck open but the mechanic is pushing the message that a cool engine is fine. But I know it will use more fuel and possibly start to affect my Catalytic Converter!

 

[WhySoSerious]

Bump

 

[JohnM100]

Does sound like the thermostat is stuck open. Does the coolant gauge go up if you are stationary for a period of time, and down when cruising at speed?

It is a big job to change it. Can you see any coolant leaks / low fluid level in the reservoir.

Those engines are designed to run hot, not warm.

 

[WhySoSerious]

Does sound like the thermostat is stuck open. Does the coolant gauge go up if you are stationary for a period of time, and down when cruising at speed?

It is a big job to change it. Can you see any coolant leaks / low fluid level in the reservoir.

Those engines are designed to run hot, not warm.

Sorry for the late reply!
Yes, when I’m at speed the temp gauge is at one bar (50c). Usually have drives through London so it’s very stop/start. Sometimes the gauge hangs around 2/3 bars but this is when I’m going 30mph for short periods of time. Then on most journeys it just remains at the coolest point of the gauge.
Goes up pretty much straight away to the 90 where it should be at then shoots back down

no sign of any leaks. Definitely not wanting to change the thermostat if it isn’t that though and from the diagnostics it’s pointing to it after I’ve already changed the sensor!!!

cheers

 

[AJB]

If you’ve got VCDS, can you leave it plugged in and reading the live temperature sensor reading whilst you go for a drive from cold?
If the temperature is jumping around crazily then something else might be going on, but if it seems sensible, but just too cold, then to my mind it is probably the stat.
Also bear in mind that the dash gauge lies to give you a false sense of perfection. As long as it thinks the temp is about right, say between 80 and 100, although I’m guessing and making up the numbers, it lies and says “exactly 90”.
With the old analogue gauges and a stat that was starting to fail, it’d sometimes read exactly 90, then suddenly jump down to 70 or whatever and fluctuate a bit, then jump back up to 90 if you slowed in traffic.