November 10th, my dad and I replaced the tailgate handle. I couldn’t open my trunk without the key fob. After that, every time I would drive I would get the “tailgate open” warning light. It would disappear when I stopped then came back on as soon as I hit the gas.

November 20th, I was about to go grocery shopping when my battery was completely dead. We figured it was the cold weather. My husband replaced it and everything was good. The next day my check engine light came on and it gave me the P0303 code. I haven’t driven it since.

November 27th, it had a dead battery. My husband went to AutoZone to get it charged and I picked it up along with new spark plugs the next day. We installed them and left the battery disconnected just in case.

December 3rd, we replaced the coils. Everything is good but I still haven’t driven anywhere. I’ve had the P0128 code for a while but have finally gotten around to fix it. We noticed my coolant was draining faster than normal. After receiving an estimate from two shops, one was $475-$500 and the other was $887.74 to replace my thermostat housing but both my husband and dad decided to DIY it. After waiting a week, the part came in today. I unlocked my car to open the hood without starting it then about 20 minutes later it’s dead again. Also whenever I'd start it then shut the car off shortly after, the cooling fan keeps on running for about 5 minutes or less.

Does anyone know what could be draining the battery? It’s a 2008 Cooper. I’m unsure what the mileage is currently at but I’m under 100,000. Any help would be appreciated!

EDIT: Mine does not have the IBS sensor.

 

@mrshyperion

The plug to ETS(engine temperature sensor) which is located right on top of the thermostat housing is not making contact therefore the fan will keep running causing your battery to go dead everytime. Inspect the plug BUT BE VERY CAREFUL, these plugs are quite brittle and breaks quite easily. If it does break, you can use the oil pressure switch plug which the same as the ETS when replacing it.

 

I bought a new thermostat housing which includes the sensor, hopefully that will fix the problem. Just waiting for my dad to get another tool he needs to proceed. I’ll let him know to be careful. Thank you!

 

@mrshyperion
When I got a new thermostat and housing with the sensor, I was assured that connector would make contact and spent 2 weeks trying to figure out why my fan kept running and draining my battery. Since my plug broke due to brittleness from high heat from the turbo, I decided to take the plug off the wires and plug the bare wires directly onto the ETS sensor and VOILA! the fan turned off immediately after I shut the car off. Let me know what your end result is.

note…… I made sure that one of the wire is insulated so no two wires touch each other.

 

UPDATE: My thermostat housing is fixed and the car is running great!