Hello, I have a coolant leak behind the back of the engine. It's coming from an opening along the bottom corner of the tunnel that humps up over the drive shaft and exhaust system. There's an area between two pieces of sheet metal that flares open to create what looks like a it could be a drain that measures maybe 3/8" by 1.5". hidden under a pice of exhaust heat shied. I see no evidence that the coolant is leaking farther forward. It an odd place so I don't want to blame it all on the heater core. The coolant just dribbles out that opening. Leak is minimal with engine off, under pressure becomes empty after 10 miles of driving. I have since bypassed the heater core and leak has stopped, so it's something beyond my bypass. Just to be safe I cleaned out the drains that were a little blocked under the battery and brake servo. As these being blocked can lead to water in the footwell. here are some pictures if anyone else is interested in cleaning out theirs the drain on the left can be tricky as taking out the break servo is a major. - Battery removed. - Under the ECU cover. - Drain under the brake servo, tricky as pipe doesn't allow you to remove it to clean it out. It's obvious I need a new heater core, as I have all the tell tell signs of this. fogging windows, coolant smell, etc.. plus the male heater core pipes are ruined. However my question is are there any other pipes/hoses coolant related that could be causing this leak into the passenger footwell and out of this drain under the car? As it would be a huge PITA to remove my dash, change the heater core and still have my coolant leak. Could it be a pipe around the centre console / transmission tunnel area or something at the back of the engine. Looking through other threads people with similar problems suggest these possible problems: aux. colonat pump coolant flange water pump oil cooler heater core I think the key to this problem is the black drain in the transmission tunnel, whatever is inside it, as this is where the coolant is coming out. Cheers, hope the drain photos are of some help to anyone needing the clean and unblock this area.