I could use some help chasing down a large coolant leak in my daughter’s 2009 Mini Clubman S. This morning she said she didn’t have any heat blowing out of the vents, and then on the way home she got the red engine light and pulled over. She had lost a lot of coolant, and was very low on oil. She said when she added coolant to the expansion tank it ran out from the engine on the passenger side. She had the car towed to our house tonight, and when she poured water into the expansion tank, sure enough it poured out of the timing-chain side of the engine. It was 18F and dark so I couldn’t investigate too closely, but the top of the engine is dry, and when I jack the passenger side up and stick my head into the waterfall of coolant, it looks like it’s coming from the under the exhaust manifold on the block, but I can’t make out what is leaking.

Any suggestions as to what up under the exhaust manifold could have failed so catastrophically? I recently replaced all the cooling hoses, so don’t think they are the culprit, but at this point I have no idea. I’m currently working on a car in my garage so I can’t get my daughter’s car inside for a few days, but I’d like to start poking around to get a feel for what I’m up against.

 

Check connecting pipe between thermostat housing and water pump.

 

Most likely the crossover pipe, could also be the water pump. Since you know it’s leaking just use water, no need to be pouring coolant on the ground, and see if it’s coming from the backside, which again most likely the case, or from the side. As for replacement, ECS has the aluminum crossover pipe and I do believe thermostat housing, these would most likely would be the route I’d go if I had too, then OEM. You have to remove the thermostat to replace the crossover pipe so just replace both of them. While you have no coolant in there, replacing that water pump isn’t a horrible idea either, this could lead to that stupid tensioner and a belt replacement as well so you can see the rabbit hole. I wasn’t a huge fan of bleeding coolant on the n14, only opened that system when I had too. It isn’t horrible, just takes a few times.

 

It’s pretty cold here in upstate NY right now and I have to finish changing the clutch on my e46 BMW before I can free up a space in the garage and investigate the coolant leak in my daughter’s Mini. I appreciate the suggestions as it at least lets me start to come up with a plan. I’ll add that a year ago I pulled the engine to replace timing gear, clutch/flywheel, and de-carbon the intakes. On reassembly I did replace the coolant pipe, all the coolant and heater hoses, water pump, drive belt and tensioners, thermostat, and aux water pump. So I’m surprised that we got this catastrophic leak. But it’s happening, so something gave out.

 

Some people cut the O-ring gasket on install of the water pipe/cross over pipe. Its easy to do as its hard to see back there and the machine cuts are sharp on back side of the water pump/engine.