Sri Lanka clinched their first series whitewash over a major cricketing nation today at Colombo as they won the third and final Test against Australia by 163 runs, with spinner Rangana Herath taking seven wickets for 64 runs.Set a formidable target of 324 in their second innings, the world number one Test side collapsed in the afternoon session on the fifth day and were all out for 160. It was the third time in a row that the Australians had lost all of their Tests in away series against teams from thesub-continent. Herath, who had claimed six wickets in the first innings, then ran through the Australian middle and lower order as the visitors' batsmen had no answer to his left-arm spin. Earlier Sri Lanka, who resumed on 312 for eight, declaredtheir second innings on 347 for eight with overnight batsmanDhananjaya de Silva unbeaten on 65. Australian pace spearhead Mitchell Starc remained the standout performer for the visitors with his 24 wickets in the series including three five-wicket hauls. The teams now head into the limited-overs phase of the tour with the first of the five one-day Internationals scheduled for August 21.