2018 Karoq 1.6TDi Overheating warning

[Comet88]

I have a 68-plate 1.6TDi Karoq, manual, currently on 43k miles, and owned since Oct 2020 (from 19k miles). It's an ex-Motability car. 

 

Since November last year, it has been generating random and intermittent temperature gauge spikes, typically up to 105-110 °C, but occasionally up to 130°C when the engine overheat warning is triggered. As it was just about 5 years old when this first occurred, I had the full belt and water pump replacement kit fitted - so, the water pump was new in January this year.  For about 6 weeks, all was fine, then the warnings started up again. Usually, the temp spikes up to around 110, stays there for about 30 secs to a minute, and then rapidly drops back to 90, and is then normal for the rest of the trip (however long that may be).

 

It's been back to the garage (local, trusted, independent) several times, they have had it on the rolling road and taken it for numerous test drives, and cannot get the behaviour to repeat itself.  Diagnostics have been downloaded, and there are no faults found. They have also surveyed the engine bay with an IR gun and there are no unexpected hotspots. Last time, the temperature sender unit was changed, but this hasn't altered the behaviour.  They think the warnings are spurious (i.e. an electronic fault), but I am not convinced.  Now booked in for a cooling system drain, flush and refill plus new thermostat.

 

There was a pattern for a while, in that the first trip of the day usually didn't trigger any temperature increase, but the second or subsequent (starting from a partially warm engine) often did, however, in the past week, I have had three engine overheat warnings on the first trip on different days.

 

Currently approaching "wits end" with steam coming from my ears - any suggestions?

[mumpsim]

An intermittenty sticking thermostat would have been first on my list of suspects. As you are soon getting that changed, I'd wait and see the outcome.

[Paws4Thot]

3 hours ago, Comet88 said:

it has been generating random and intermittent temperature gauge spikes,

Is the expansion chamber labelled "mit silikat"? If so, then get that changed for one not so labelled next.

[SuperbTWM]

Unplug the connector on the water pump to stop it actuating the sleeve, I know it has been replaced but that would rule that out completely.

[Sanqhar]

21 hours ago, Paws4Thot said:

Is the expansion chamber labelled "mit silikat"? If so, then get that changed for one not so labelled next.

This is the "Mit Silicate" problem (Feb 2023).