I have a Volkswagen LT35 2.5 TDI which has been running well until it started making a tapping sound intermitently, however i came in after a run and found that when the van was at idle its sounds really rough and tapping however when i rev the engine the noise goes away, i drve the van again to see if the power is there and it is but soon as i idle it the horrid noise comes back, since then i took the front timing cover off and found that the timing belt was really loose, so suspect its slipped some teeth, the van still runs but im not going to and revs up with the noise going away, it think its slipped a couple of teeth, how likely is it that theres valve damage? am i likely to got away with it and can put a new belt on it and tensioner?
these LT engines don't normally run if the timing goes a fraction out. I suspect the culprit is the brake vacum pump. When they get noisy they sound awfull! they bang & clatter something chronic.
I would get the belt fitted by an expert unless your really confident to fit yourself.
Just out of interest ID, a mate who had the 'pleasure' of doing several of these (and successfully changed no5 glow plug...respect...tried meself without success on the engine in my Volvo once) told me that the camshaft pulley had no woodruff key for locking to camshaft and relied purely on the tightness of the locking bolt, and the essential use of a proper timing kit to set the belt position.