It's leaking coolant behind the pulley system?

Hello,

It is probably more likely a the water pump leaking. It could be the head gasket. Usually when a head gasket leaks you will have excessive white smoke out of the tail pipe. Unless you have white smoke it is safe to say the water pump is what might be leaking.
Do you have overheating issue? Another symptom of head gasket leak. It will also make the oil milky in color due to mix with coolant.

https://www.2carpros.com/articles/coolant-leak-symptoms

In order to replace the water pump you will have to remove the drive belt. This can be done using simple hand tools.

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.