Sounds like tappet / lifter clacking - page 2 - Troubleshooting - VWDiesel.net The IDI, TDI, and mTDI source.

• #15 by Zulfiqar on 09 Sep, 2009 22:20
• upon rebuilding a hydro head I found that its bucket oil galleries were sludged up and one time fixing a suzuki G13B engine its also a hydro head 16v I found that the oil pan was dented badly choking the oil intake.. hence low oil pressure in the head.
• #16 by jtanguay on 10 Sep, 2009 16:29
• i had some bad lifter tick a few years ago while going to work (my 1.6TD hyd) and it was caused by lugging the engine at 1000 rpm (might have been lower actually) and then the lifter tick was very pronounced, and didn't go away.  i pulled over... nothing obvious but the tick, so then i gave it the old italian tune up and bingo, noise gone  i'm sure it was oil pressure because the engine wasn't spinning very fast at the time...
• #17 by smutts on 15 Sep, 2009 12:01
• Quote

  Grin new camshaft for £34 on fleabay

  
  http://cgi.ebay.co.uk/Volkswagen-Audi-1-5-1-6-Diesel-Camshaft-C109_W0QQitemZ220465755567QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item3354c875af&_trksid=p3286.c0.m14
  
  Too simple! I just got an apologetic Email and refund as yonder camshafts are outwith where they thought they were.
  
  SO! I don't suppose an AAZ camshaft will work?