Question on Cooling System Leak Test

I have a 2009 Mini Cooper S Hatchback with 64.800 miles. Three weeks ago the water pipe exploded, the car overheated and started to shake/misfire. I scanned the car for error codes and I found the codes P0105 Can�t Measure Air Flow, P0217 Engine Coolant Over Temp and C3617 Unknown Issue. I replaced the water pipe and vent hose, cleared the codes and the car was running fine. A few days later the car misfire and had no water in the reservoir. I scanned the car again and found the error code P0117 Engine Coolant Temp Sensor. It leaks water only when the engine is hot/warm. It looks like the water is coming down from what I think it is the AC drain hose under the passenger seat, but it cannot be because with the AC off water still comes down. I replaced the water pump 6 month ago and in 2014 the Thermostat Housing. What could the problem be? Any suggestion would be greatly appreciated. Thanks.

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This post was auto-generated based upon a question asked on our tech article page here: MINI Cooper R56 Cooling System Leak Test (2007-2011) | Pelican Parts DIY Maintenance Article

[Nick at Pelican Parts]

Sounds like the heater core is leaking.

- Nick

[Ferri208]

Yesterday, I filled the reservoir tank all the way to the top and I drove to a friend's house (about 20 miles away). When I arrived, I looked under the car and the car was leaking water by the Exhaust Flex Pipe (front pipe). So based on the location of the leak, it was leaking from the back of the engine. Almost an hour later, we lifted the car, placed two jack stands, checked under the car and there was no leak. I started the car to make sure that the engine was fully warm, I went under the car again and no leak. So I removed the intake air housing to see if I could see any signs of a leak by the thermostat housing and/or water pipe and I couldn't see anything. If there is a leak, it should always leak. This does not make any sense to me. Do you have an idea of what to do based on this info to determine the source of the leak? What should I look for to determine if it is leaking from the heater core?

Thank you very much for your help. I really appreciate it.

[Luccia at Pelican Parts]

If it was a heater core leak, you'd definitely have coolant on the inside of the car. The thermostat can leak and pool on top of the transmission. Check on top of the transmission for any signs of coolant. If you still see nothing, I highly suggest pressure testing the system, which is shown in the article you posted in. Thermostats fail on these cars, more often than not. Make sure the water pipe is properly installed as that can pose an issue as well.