clicking coming from rear hatch

hi again. another problem from our pece of junk :naughty:

anyways, every now and then (only when the car is first started) there is a loud and fast clicking noise coming from the rear area of the van. it happens rarely. and most of the time it only lasts for a couple seconds. one exception was about a week ago when we were on vacation where it kept clicking until the van was shut off. started it back up and it didnt do it.

the only thing i can think of causing it is the rear wiper or washer, but both of them are shut off and the rear wiper hasnt been working since about last winter.

any ideas?