My D2 has just started to do the same (or similar). It seems OK for ages and sits at 90C, but when I slow down or get stuck in traffic, it starts to rise. Get it out onto a 70mph stretch and it's back to 90C again.

But in slow, uphill driving it gets above 95C (but not quite 100). Both fans are running and the thermostat is recent - so back to the garage that fitted it I suppose.

Would a CTS fault show upon VCDS?

Yours seems like it could be genuine reading, temperature rising when load is higher or oncoming air speed lower.

When my stat failed recently the indicated temp climbed to 100deg plus as you would expect. However, when putting vcds on at home and starting the car, on one occasion the indicated temp showed a steady 95 when vcds show it steadily climbing to 100deg plus. I didn't manage to sort out why there was a discrepancy but it did occur on two occasions when I was trying to see if vcds could reveal any other defect. E.g pump or CTS failure. The stat is stamped as "87deg" so that is obviously when it should open and get the extra cooling of the radiator. The electric fan seemed to kick in at or around 97deg - a fact I ascertained when waiting for the engine to cool down when nursing the car back home after the stat failure. I.e. It would stop working when the temp fell below this as indicated on the dash instrument.

Nothing on the VCDS scan, but I've not seen this behaviour before - the gauge usually sits at a very constant 90C. The pump and thermostat were replaced when the belt was done earlier this year, so if it's either of those, then it's a warranty job.

My suspicions are that it could be due to a sub-optimal pump that isn't coping with the slow speeds and extra load.

Booked in on Monday.

I fell your pain ..hope that it works out ok , gets sorted ok and not to much ££.

Had mine done now ...so will see how it goes.

good luck with yours