Changed the oil in the S this weekend and everything was fine as it had been every time before. Yesterday the wife was going to the store and noticed the check engine light on so she put the car back and drove another. I am thinking this can't be good but why would the light come on so I check the oil and it is still perfect. Then I notice the coolant bottle is empty. Looked under the car nothing but it had been sitting all weekend. Felt under the bottle and seemed to be dry so where is the coolant going? I took the car out to the shop and put up on ramps, filled coolant back up and cranked car and let it run until it got up to temp. I noticed a drop or two on the floor right in the middle of the car right at the back of the motor. I felt around on all the hoses and could not find anything wet and the hose under the bottle was not wet so where can the coolant be coming from. Apparently when I moved the coolant bottle to move the oil filter something must have loosened to allow a leak but for the life of me I can't seem to find it. Has anybody else had this problem and if so please let me know as my wife is now afraid to drive her baby.

 

The water pump is on the passenger side near the back of the engine. Just changed mine out because it was leaking....when it leaks, it drips onto the undercarriage and then to the ground....kind of behind the engine. I would check there. If you look around the pulley, it will probably be obvious that its leaking. The other common leak point is at the thermostat housing on drivers side of engine. Good luck.

 

This happened to me a couple weeks ago. Leaking coolant from behind the engine. My thermostat broke. It was a simple fix. Happens to most minis.