checked my header tank last night, when I opened it, it was full of froth, looked just like fairy liquid, bit alarming.

ive heard of people putting it in to prevent the mayonnaise of a pourous head, but it doesnt smell or taste(!) soapy, and would it still preventthe build up after 2500 miles and 5 weeks? engine tempretures are fine, and heres nouthing unusual under the oil cap.

anyone got any ideas? could it just be an airlock?

going to flush it anyway to be sure.