There is only one way to do that job properly and I doubt any of you guys have ever heard of it. Check out Liquid Intelligence radiator and block cleaner
http://liquidintelligence.com.au/pro...m-cleaning-kit
My brother in law has just used it and I've seen the results. Unless I had seen it, I wouldn't have believed it. The pictures on their website are not doctored.
I have absolutely nothing to do with this company. Any prices quoted are in Australian dollars. One $A buys about US75c