2018 JCW with just over 21K miles. Stock. Well maintained. Driven but not thrashed.

Drove home last night and in the heaviest rain the car has ever been in. No problems. Got home and backed car into car port. Let engine idle some and was enjoying the heater prior to the cold walk from the carport to the house. Rain water dripping down on the front of the car. Noticed water vapor wafting up from the front of the car.

No signs of any cooling issues. Checked the coolant "gauge". That thing would have to gain about a zillion IQ points to qualify as an idiot light. Geesh what a lame *** piece of hardware. At any rate it showed "OK". Checked for any issues via iDrive. Except for nagging me about the engine compartment being open and the engine compartment being hot and there was a danger of burns -- half expected to tell me to stand up straight and eat my vegetables too -- nothing about engine coolant over temperature or low coolant level.

Thought the vapor might the rain water on the hot radiator, inter cooler, oil cooler. Did not detect any odor of antifreeze but my sense of smell is subpar due to recovering from a sinus infection that caused olfactory nerve inflammation which caused everything to have a chemical smell.

Engine was too hot to try to check coolant level last night.

Ok, this AM with everything cold checked the coolant level. On the bottom of the tank just two small plastic blocks of different heights. The shorted one labeled "Min" the other "Max". Not even an inch difference in height. With the engine off I added not even 16 ounces of water and the level was just up to the Max step. That didn't seem like the cooling system was that low.

Started engine and no sign of any leaks. Drove the car around and got it nice and warm. Back home parked the car and raised engine RPMs to 2K and held them there for a bit. Coolant "gauge" didn't even budge. Wanted to hear the radiator fan come on but it never did. Shut off engine and walked around car. No signs of any water vapor and it is cold enough: 34F; that it would be obvious.

Going to stop in at the MINI dealer on the way to work and see if I can't get the car lifted up and have the tech check for any leak sign. Right now I'm thinking the vapor last night was just rain water on hot engine components. And this AM the low coolant level just normal. I have to admit I have not bothered to check the coolant level since I have bought the car. I got spoiled with my Porsche cars. The coolant tanks were huge holding nearly a gallon of coolant and in 16 years and a combined nearly 500K miles the low coolant level only came on two times and that was from a bad coolant tank cap that when the coolant was hot would allow vapor to escape which would cause the system to loose about a gallon of coolant in a month. The low coolant level would come on. Second time I did some investigation and found the cap to be the culprit.

Just got back from checking the car after letting it sit for a few minutes after shutting it off "hot". No signs of any leaks. Coolant level right were it was when I added some water this AM. As I loosened the cap there was a bit of pressure released so the system appears to be pressure tight which is a good sign. No odor of antifreeze. I stuck my face down as close as I could to the gaps between the engine and engine compartment and no antifreeze of hot oil smells at all.

Guess I'm just checking in to see if there is a known water pump or hose or radiator weakness that has these cars prone to a coolant leak?

 

Update: Drove car 10 miles to dealer. Spoke with SA. He said they like to keep the coolant level between the Min and Max levels. Based on what I could see that's about 8 or so ounces of "room"...

He went on to say had the coolant level gotten really low there would have been a warning light and had the coolant temperature climbed too high a warning light for that too.

During the drive in I saw no signs of any cooling issues. The car was fine the entire 30 mile drive to work this AM. At the office as I was unloading the car I smelled no odor of antifreeze. Saw no signs of any coolant leak under the car.

I'll keep tabs on the coolant level for a few days but I believe the water vapor I saw last night was just rain water coming in contact with the radiator.

 

I notice when it's cold outside i can see faint traces of "steam" from the front of the car - had this before on VAG cars - nothing to worry about it's normal