I also have a ticking noise on the driver's side engine compartment. It seems to be coming from some sort of valve with some plastic lines going to it. Funny, b/
c I thought it was a lifter or cam at first, because it sounded real loud the first time I heard it parked against a wall at my local drive-up ATM. There is also a plug going to it.
It sounds like a dampened rubber metalic clicking.