2012 Superb.

Suddenly getting 2 unusual events, possibly linked.

1) the water temp doesn't reach the mid point on the dial like it used to.

It will go up to around 80 degrees, and then back off. Never reaches 90 like it did. Its usual tem now is 70.

I've rebooted the Aircon twice.

Air heat now fluctuates with the water temp - as expected, but what's causing the engine to not reach operating temp?

Thermostat?

Turning up the warm air temp to the car causes a quick drop in dial, and Oil tem drops too.

2) For years i've sat at 750 rpm on idle. Now I get 950, but restarting the car sets it at 750.

All ideas welcome!

Need more info on your car. Engine? DSG?

Are those temps at car own gauge or obd?

Idle is too high that 750 is correct.

More info.

Car is 1.9 TID DSG. 82,000 miles.

Idle revs have always been 750 until now. When the engine is started from cold, it revs at 950-1000. After a short drive, restarting the engine sets it back to 750.

Temperatures are from the Temp gauge - confirmed as working, and Oil temp from the screen readout. These have been checked with a plug in diagnostic panel.

Really "gunning" the engine is Sport mode will get the the water temp up a bit higher than 40 degrees, but putting on the car heater fan makes it drop quickly.

How difficult is it to fit a new thermostat?

There is also a thermostat for the DSG (hence my question!) which can fail. If that fails open, coolant will be circulating through the DSG cooler all the time, and this will cause your coolant temperature to remain lower than it should to a certain extent.

I believe it’s a reasonably straightforward DIY job with plenty of YouTube videos out there. A genuine one is around £40-50, but it looks like you can buy third-party parts for considerably less.

Could still be the main ‘stat, and I’m not sure how you distinguish between DSG ‘stat failure versus main ‘stat failure.

Here 1.9 unit injector engines were available only 2010 and older superbs but if you have it main thermostat is easy job versus 2.0cr engines

Thanks guys. All good Intel.

I will replace both thermostats as bits need to be taken off anyway, and it will save revisiting the issue I hope.

Someone on YouTube described my problem and it was the DSG one as the issue was still there after an engine thermo replacement.

I will update when it's done.

My old Norton Dominator 99 Cafe Racer is a lot easier to work on!