well,after finally narrowing down the clattering noise that was getting worse daily to the crank pulley failing i decided to change the pulley.
i got a pulley off ebay for 62 quid(2 year warranty) and new bolt and washer from rimmers(clearance bargains)Rover 75 Bolt - Flanged Head - Crankshaft Pulley - Genuine MG Rover at www.rimmerbros.co.uk
bought 2 at that price in case i ever need another...cost more in postage than the cost of the bolts.
anyway...after searching this forum i fired up my big compressor and oiled up my h/d 1/2 inch drive air gun and set about the bolt...no good at all,did not budge it...got my 3/4 drive bar out and tried the lock the bar against the lower arm and hit the starter...over and over...just dented the arm...this was yesterday...today i tried to find a 3/4 drive air gun for sale locally but no one had one in stock...after a bit of head scratching i had a plan...i called a mobile tyrefitter friend of mine and he came round with his van after work tonight...he rolled out his snap on h/d 3/4 drive gun and all we managed to do was break my adaptor...so...he rolled out his 1 inch square drive air gun(the one he uses to whip off truck wheel nuts)and it took almost a full minute before the bolt finally gave up and came undone.
i have been a truck mechanic most of my life and cannot remember a tighter bolt!!
anyway..i now have a relitivley silent td4 engine at last.

Wow.. glad mine was done a few months before I bought it!

Thanks for the info Chaps..

Other than the clatter noise, is there anything visual to look for?

Cheers

Wobbling crank pulley....

metal swarf around the crank pulley area looks like angel dust ,use a torch and you will see it more visable

yes,mine was throwing up metal dust where the 2 metal bits were rubbing together and making a clattering noise which got louder by the day and just before i changed it i thought it sounded like the big ends had gone it was that loud.
the metal dust was visible under the bonnet as the belts and pulleys were throwing it up all around the inner wing.

never be tempted to use any other pulley than the one meant for the job ,as it has a damper in it ,without it you will break the crank

right....update time....
the e bay pulley i bought was ok till about 3 weeks ago...completely fell apart...the rubber delaminated leaving the crank boss in place the rest of the pulley was clattering on the chassis...recovered by AA.
the pulley came with a 2yr warranty so i contacted the seller who told me to send it back for a refund,i got the impression mine was not the only dodgy pulley he had sold.
so...needing a new pulley to get me back on the road i called rimmer bros,told there were 3 options...cheapest was just under £100...the oem was about 160 and the dearest was well over 200 quid,so being a tight git i bought the cheap one,i fitted it and exactly 1 week later it delaminated!!!!not as dramatically as the first,but wobbling and rattling about.the cheapo one was of course BRITPART.
so i called rimmers and have now opted for the oem pulley.they delivered the new one postage free and collected the faulty one so good service unlike the ebay one that i had to return at my expense.
so im hoping this pulley stays in one peice?

wow, you have had some bad luck, and yes those pulley bolts are very tight