ok dawn does not do crap for foam if you reallly want to foam you need to go out and get you some amonyx-lo it is a neutral foaming agent (only makes foam does not clean), then you go out and get you some potassium hydroxide flake and some sodium hydroxide flake. now you get a 5 gallon bucket and put 5 cups of potassium 5 cups of sodium and about a cup of amonyx in there and the rest water now if you cant get that to clean then you are crazy.
That's a pretty hot mix, 10 cups of caustic to 5 gallons of water will do some damage. My standard mix is half of that, but juicing up for asian or neglected systems works well. Not sure what amonyx is, but industrial dawn works pretty good if the mix isn't too hot.