One of the forum members here told me about Snoop leak detector. Amazing stuff. I was trying to trace down a very slow leak in my MK4. Tried different solutions of soap with zero results. Got some Snoop from Amazon and detected the leak right away.
its all in the method with soap .. dish soap works good with id say about 1:5 ratio with water, mix alittle in a cup and dab it around threads etc with a qtip .. cover the critical areas good but not too much, dont keep soaking it .. have it under a good light, and actually as it 'starts' to dry it will become tiny bubble city on a slow leak ..