Hi Folks,

I'm the owner of a 2014 Mini Countryman S R60 hoping for input on an issue I'm having. Last winter after the car sat parked for a few days at an outdoor temperature of about -5 degrees F(-20.5 C), my check engine light came on with a P0128 for low coolant when I drove it in similar conditions. When the weather warmed up a little I cleared the codes and had no further issues until this winter when we took the car up to the mountains. It sat parked for 2 days in sub zero (F) conditions, and when I next drove it the outdoor temperature was about -17 degrees F(-27 C), with heavy wind, windchill was rated about -38F. The check engine light came on after a few minutes. Also in these conditions, the climate system produced almost no heat, barely enough to run the windshield defroster, and it did not keep it complete free of frost. After a few hours of shivering in the car, we reached a point where the outside temperature was about 0 degrees F(-18 C). By this point the heater had gradually come up and was producing enough heat to keep the car comfortable. The check engine light remained lit.

I'm debating whether I should replace the coolant thermostat. It seems to work except under the very coldest conditions. Is it possible that the thermostat is leaking slightly in the closed position? Is there something else I should check first? Do you folks think the heating system should be able to perform adequately in these conditions? Any thoughts would be appreciated!

Thanks!

MC

 

Error Code P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature).

This error can appear if the engine coolant temperature doesn't reach some threshold after so much engine run time.

While a stuck open thermostat is possible be sure the coolant level is good. Do not overfill the cooling system but bring the level up to a known good level about mid way between the Min and Max levels..Remember when the coolant is at temperature the level will go up.

Given how cold it got you want to be sure the coolant can resist freezing. While freezing solid, at least in the colder parts like the coolant tank, is probably possible more likely the coolant, at least in the colder areas, can turn slushy and this can possibly interfere with proper coolant circulation. Hard to imagine though this condition could persist for long with the engine running. Still be sure the coolant strength is such that the coolant is safe down to -40C. (This probably requires a 50:50 blend of anti-freeze and (ideally) distilled water.)

A check needs to be made that the engine coolant is circulating when the engine is running. One technique is to start the cold engine and every once in a while check the hoses downstream of the T-Stat get warm then hot as the coolant temperature climbs and eventually -- the engine speed may need to be elevated a bit above idle by using the gas pedal -- the T-stat opens. Concurrently with checking the hose temperature one can -- with the proper equipment -- monitor the coolant temperature as the engine controller receives this voltage signal from the coolant temperature sensor. The coolant temperature wants to climb about 1 degree F every 1 to 2 seconds at regular idle speed.

 

Thanks for the detailed reply RockC. I'll check out the coolant as you suggested and report back. We flushed the coolant last summer, so the level was set then, if it's down perhaps I have a coolant leak, good call to check this. Thermo job is at least a few hours which I don't really want to do in freezing temps, so I'm willing to give pretty much anything a try first.