Q. Are there any circumstance under which a coolant temperature of 174-176 F (79-80 C) would be considered 'normal'? (car is R56 Justa 7/2010)

Yesterday: hot day (mid 90s), AC on and driving hard. Looked over at my UltraGauge, and noticed my coolant temp was running about 176 F (80 C). Normally, after warm up, I'm used to seeing temps in the 210-222 F range (100-105 C).

Today, on a short drive around the neighborhood, observed temps were as expected. That is, got up to 220 F (104 C), so I know the system is capable of normal operation.

The MINI's OBC is not showing any abnormal icons or errors. The UltraGauge has some (limited?) ability to read Trouble codes, but none found.

My Bentley's says "If the ECT sensor input is faulty or not plausible … the ECM assumes a substitute value (80C / 176F) to maintain engine operation."

I've also seen references to the thermostat having a "high flow" position which drops the temp under high demand - but I don't know if that means it drops to normal (200-220 F), or below normal.

Some say the ECM drops the operating temperature to about 188 F when the AC fan is in the Max position, no matter what - possibly only in Sport mode - but less clear about Justa vs S models, which model years, etc. I don't believe my AC fan was on Max (not sure), but I did have the AC button on which recirculates air (vs outside air), and I was in Sport mode.

Q2. Is it likely that I have a faulty temperature sensor and/or thermostat, or could it possibly be the ECM temporarily went into some kind of emergency mode, and all is working as expected?

Q3. Is it possible/likely that there may be error codes which could only be found with a more sophisticated scanner? My nearest MINI dealer is 200 miles away, so that's out. I do have a very well equipped, modern repair facility nearby; can I assume their scanner is probably not the same one used by MINI dealers, but would be capable of reading MINI error codes?

 

I think that the AC on is why the coolant is around 175F.
With AC off on a hot day, the coolant will reach the 220F (you could test this).

 

Have done. In my case, the temp was dropping, even when driving like an old lady with the AC off.

Just had my thermostat replaced ($640!) and now operating as expected.

 

Woow! Sorry for the price! but Im glad you have your car running as expected.
Enjoy!