106 gti engine rattle

Hi, this is my first post.

I have a 106 gti that the engine rattles from time to time, normally after the car has warmed up - it is a whining rattle that comes from the timing belt area/16v box. Possibly, but not definitely air escaping. The car is running fine, I had the timing belt changed about

I have had a mechanic take the cover off the belt and have a look - he says everything is fine in there. What else could be making this noise?

Any replies much appreciated - I am worried about my cam belt going then the engine going BANG, don't have the cash for a rebuild want to get it sorted ASAP.

Thanks, ben.