The timing belt tensioner on my early-2005 Golf 1.6l FSI (50k miles on the clock) "sticks" when the engine is started from cold, apparently the tensioner tightens the timing belt when you start the engine, and then pops back in, however mine's not popping back in quickly enough. As a result, it makes a nasty clicking sound as the engine turns for the first few revs.
It's done it for a few years, on and off, depending on how recently the car's been started and the season, but has never got worse, per se. Lubricating it does alleviate the problem for a week or two but it soon comes back.
The repair cost is astronomical (since it involves removing the engine entirely, apparently). Is it worth it? The chap who serviced it last said it's not an issue unless it happens while the engine is running and has been for a while. Is this valid?