My coolant temp looks like this:

enter image description here

It fluctuates, but never really goes much higher than the first bar. It's not really been a big issue for me, better cold than hot, however the cabin heater has gradually been getting colder and colder as well and now that it's almost winter I'd like to get this sorted.

I'd like to possibly diagnose this myself.

There are no errors on the dash, or warning lights.

Coolant reservoir is full, no fluctuation in coolant level.

The radiator fan isn't on, nor have I heard it come on.

The radiator was replaced last year with new coolant and the system bled. It was fine until about 2 months ago when the water temperature started to slowly drop.

The car is an r52, 2005, Mini Cooper Convertible. 110,000 miles.

No other running issues or faults.. just cold engine, and cold cabin heater.

So yeh, what would be the best course for diagnosis? Is there a hidden dashboard menu with any diagnosis stuff like coolant temps? Could I buy one of those cheap code reader things off ebay and plug it in? Can I remove anything like thermostat or radiator temp sensor to check?

  • My first bet would be the thermostat. It's probably stuck open. IIRC, these have a composite unit, with the thermostat built into them. Not able to look it up right now as I'm on my phone. I think I did an article on changing these out earlier this year. Commented Nov 5, 2016 at 22:57
  • I last worked on my wife's 2005 about two years back, but remember the cooling is a bit annoying to work on. A good copy of the BMW/MINI TIS on CD is a must for do it yourself. Commented Nov 5, 2016 at 22:57
  • 1
    See if this video might help you. Commented Nov 6, 2016 at 4:18

1 Answer 1


sounds like your thermostat is stuck open. I would check this first.

You might be able to squeeze the hose going to the radiator and see if you can feel water passing, while the engine is just started and still cold. You should feel very little to none. If you feel a lot then most likely the thermostat is open when your engine is cold which is not good.

The only other thing I can think of is your in a place that is so cold it's basically air cooling your engine but this is not likely.

  • 1
    It was fitted with the wrong thermostat when I had the thermostat housing replaced. Replacing the thermostat with the correct one fixed the issue.
    – StuR
    Commented Nov 29, 2016 at 17:39
  • @StuR That would do it. anything that will let water leak around it will keep the engine cool
    – Cc Dd
    Commented Nov 30, 2016 at 3:17

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