Coolant sensor STOP message

[wazevan]

hi all,
I know its hot but yesterday was out in car 20 mins ,as I parked up and turned engine off,i needed to straighten car up.Turned key (before engine start) and message came up on dash,it was temperature gauge  pic and then message said coolent and then STOP. I turned engine over and it went and temp gauge went back to normal. When this happens the temp dial goes from 90 to 130.
This is happened twice today ,but only as above not driving.When I first drive the temp dial goes betwwen 50 and 90 then settles at 90 (normal). No leaks or fluid loss.Car driving as normal,heating working normal.
Bit gutted just had mot done and was chuufed it only needed minor things(tryes,pads)nothing in engine bay.Hoping its a bad sensor(looks a bugger to get at) Any ideas thanks in advance

[johnnyroper]

If it was me I would just monitor for now so long as it donââ,¬â,,¢t actually overheat.
Been having similar with my Alfa in this extreme heat,keyed in to checked fuel level and did not start it flagged excessive rad temp and DPFclogged on display. Took key out and bag in then started and it was fine. I have put down to the temp inside car making controllers have a fit.

[brianh]

That sounds like the sender on the thermostat housing has failed - the temp can't raise 50 degrees just like that. It might be the connection to the sensor rather than the actual sensor. There may be more than one sensor, so you might want to unplug them one at a time to identify which one is driving the gauge.

If its truly that hot, you will usually know by other signs anyway, also given that it was when you went to start the car it can't have got hotter whilst parked without the engine running (not that much hotter anyway!).

Have a check of the water level in the expansion tank - Theres a sensor on the bottle (at least on the petrol ones there is, think the diesels are the same), it may be triggering it because of that.