Images?

Here is a diagram of the rear if you don't have VIDA

 

You say rear of the engine, is it anywhere near the transmission end? The PCV hose, the heater hoses, the main metal tube that runs under the exhaust manifold could all be culprits. Start removing parts until you spot it.

 

I'll bet the leak is coming from the thermostat housing, it's really hard to spot as it's under the power steering pump. Mine started to leak out of the blue too, replaced the whole thing, thermostat and housing as it's sold as one piece.

 

I second the thermostat housing. Had one there myself. Also check the actual coolant reservoir where it's connected to the hose. Took damn near everything apart before I realized the reservoir had a small crack.

 

Thank you for the replies everyone.
I think I will have to pull some parts to try and find where it's coming from.

For the thermostat housing, would it leak all the way back to near the angle gear? Seems like a far route to make it there.

 

Check hoses 9 and 10 in the above diagram.