i have a 2004 discovery. i've had many coolant leaks throughout the system. now i have a leak behind the engine. it doesn't seem to leak until i turn on the heater. there's no leaking in the cab on passenger side. the coolant is not milky looking. i've read the different forums and i guess its the "valley gasket" or the "heater core." does anyone have any suggestions. has anyone used a small camera?

 

Im thinkin head gasket.Thats where mine started leaking.Try using a telescoping mirror and flashlight.

 

oh a mirror! i'll try it. thanks. would the leak more likely be on the back right or back left of the engine? the green coolant appears to be collecting on the rightside, looking at the grill