Hi guys, Im just in the process of buying a V8 xjr, I own an audi S8 which ive had for several years but have allways liked the V8 xjr after driving one a few years back, I looked at the car and it seems to be looked after apart from the usual rust problems on arches etc, its covered 140k but on start up I noticed a knocking tapping sound which comes from the top of the engine nearer the back ( near windscreen) when the engine is revved the sound doesnt get louder and infact the engine sounds very smooth, and the car performs well and pulls great and is smooth etc, Im aware of the tensioner problems and niskali but the seller assures me the cars been like this over a year and hasnt bothered his and he recons the sound goes away once the car has warmed up, which again leads me to believe chain tensioners could be cracked etc going on what ive read online! Does anyone have any idea what it could be, as ive read that with the tensioner the tapping or knocking sound goes away after a few seconds on start up but this doesnt seems to stay for at least 10 to 20 minutes. Thanks

 

Knocking near the back sounds more like supercharger versus tensioners. Mine had a failed lower tensioner, very noticeable from the front of the engine.
If the SC belt is removed and the noise is gone, there's your issue.

 

Thanks avt007, I will defo have a look at that, is it easy to remove the sc belt? and is it safe to run the car without it? Thanks again