[Ronbo]

The dye may be reacting with the water-wetter. You could try the same mix in a mason jar and let it sit for a few days then see if any pressure develops. (throw a chunk of aluminum and iron in there as well) The dye was probably never tested with the water-wetter for issues in the first place.

What was the initial problem that you put the dye in for? (this may have been disguising the head gasket leak if there is one)

Also have you re-tourqed your heads recently? (do this first)