Suntank Solar System has not worked properly from New

<p>I had a Suntank Solar System installed at my house two years ago. The system works for at most eight weeks and then the pump starts making trickling bubbling sounds and if left eventually stops working. Suntank have been out repeatedly to rebleed and look for air leaks and I am assured that it is fixed. They last fixed it exactly four weeks ago and it is now faulty again.</p>