It is WAY too muich trouble to change a pod just because you SUSPECT that it is bad. You should properly diagnose before replacing the pods since it is about a 15 hour job.

Remove the glove box liner and you will see a vertical manifold at the lower left of the glove box opening. Remove the lines top to bottom one at a time and use an auxilliary vacuum source to see if they leak. If you find one or more that leaks and it is NOT the defrost pod which can be changed without removing the dash, then buy ALL the pods and replace all of them while it's apart.