rattle from engine!possilbly timing chain?

hi guys have a problem i hope you can help me with,i have a 2002 td4 fl and have a rattle from the engine,
it is coming fron the front end by the belts.i have the under tray and guards off and nothing is catching,it is not the water pump and the crank pulley seems ok.and it only happens under load.
under hard acceleration and above 3,000rpm it is very noisey and sounds almost like there is no oil in it.(and yes there is oil in it i checked!)
i am beginnig to suspect the timing chain tensioner or chain is worn but on checking these forums and on the net that is not a common problem.
not sure of the mileage as it came from a breaker but he assured me it had come out of a fl with only 20,000 on the clock.
not sure if he missed another zero off the end or what!!
on reading the haynes manual it seems to be a big job with the engine out head off and the sump off aswell
can the chain/tensioners be checked in situ,or is there any way to confirm it is chain or tensioner b4 i hoik the engine out?
any help would be greatly apprietiated as it is gonna be a exspensive time consuming job by the looks of it
cheers
darren

Could be the rubber/bonding of the crankshaft pulley has broken. In the right area and lets the pulley bang around.

Check for cracks in the rubber. There has been a thread on it earlier.