Description Reviews Has coolant been disappearing? But you can't see where it's going? There are three common places on the Generation 1 MINI Cooper S that it could be going. The expansion tank is leaking, the thermostat is leaking, or the water pump is failing. It's very hard to see up into this water pump and you need to be under the car, take of the under tray, and look up with a flashlight. You will see a green caked up area under the pump and on the block. If it's really bad it'll make it all the way down to the bottom of the oil pan. This water pump is on the back of the supercharger, so that's going to have to come off, and it's a good time to check the fluid and do a flush of the supercharger oil. You should also replace the small o-ring (item #2 in photo) that lives behind the neck (item #3 in photo) that the water pump goes into on the block. The water pump already comes with a new o-ring that goes into that neck. This is the newest up to date part made by Saleri. While this pump is an aftermarket pump, this is the same manufacture that makes the pump for MINI! This is a bigger job that will take some time, and we highly recommend a Bentley manual, but basic hand tools will get it done.