Hello all,

Long time lurker (4 years) first time I had to post...

My girlfriend has a 08 Cooper with 76k on it... N12 motor. Just replaced the water pump and bled the coolant. Got it up to temp by driving around, parked overnight. Topped off fluid and was fine for a few days. (I replaced water pump due to coolant drops on ground as it was slowly leaking)

Fast forward 2 days and we are in the middle of a 450 mile one way trip to the upper peninsula of Michigan. Driving on expressway, AC on... Coolant temp warning, pull over immediately.Coolant level still in the middle of resource... Wait half hour.. Then go

Happens again so I pull over and unlock the hidden menu... Test 7, see all little "t"s then °C followed by numbers constantly changing... From 70-110 °C triggers my warning, then it goes away and repeats. Sometimes it settles at 82°C sometimes 100. (Cruising at 70 with heat on and Windows open)

I'm like 300 miles from home, nervous, sometimes the fan was on when we stopped, sometimes not. Thinking coolant temp sensor died or thermostat? Any immediate help appreciated
Thanks

 

Seems plausible there's air still in the system.

 

Any codes thrown that you can check?

 

I will try to bleed soon as I can, ok to do it hot our wait til cool?

Yes there is a check engine light that recently came on. I do not have a scanner with me... Inpa is at home on my laptop

Driving with test #7 and ctmp is constant "t" or *** since I started thread

My gf and I thought this was the more reliable car and made me leave my bmw m5 at home... This will teach her lol.

 

I would wait and let it cool, don't get any do overs on hot pressurized cooling systems.

 

There's no leaks or anything that you can see? If re-bleeding it doesn't work, if/when you can safely get to a place that can pull the code, it may help give us an idea to what could be going on.

 

No leaks, it was parked for a good half hour and no drips. Coolant reservoir still same level.

Will pull codes soon as possible, don't even see any auto zones/ advance auto parts etc up here in northern Michigan... So might be a few days but thanks for the input thus far

 

Is the 2 stage fan working ? Ac on did high speed fan come on?

Sent from my iPad using NAMotoring

 

Try turning the heater on full blast for a bit to open up the circuit.

 

Didn't forget about the thread... Just got home last night from vacation. Ordered a coolant temp sensor and it was waiting when I got home.

Popped it in and no more issues.

What a relief!

Thanks for all the input

 

Those plastic coolant temp sensors are known to go bad, glad it was cheap and easy for you to fix. I also recommend having a spare plastic reservoir cap because those go bad as well. You got to hate those plastic parts!

 

Great! Glad it was a simple fix. Safe travels.

 

Sorry to be dredging up so many old posts. Would you be so kind as to elaborate on the symptoms of the "bad" reservoir caps? I'm trying to find a possible leak and am concentrating on the reservoir tank - there are cases of these cracking/splitting. I don't see any indication of this being the case, but was wondering how the tank will vent excess fluid. I know how the old style caps push up a spring load but never seen a cap like the one on the Mini before. Live and learn???

Thanks in advance for any insights you might be willing to provide.

 

You can probably try and do a pressure test on the cooling system to see if there are any leaks. Technically the system should be airtight.

 

Thanks for the suggestion, I will give it a try.

Rob