Tapping noise from belt/ pulleys?

Hello guys and ghouls... Just changed the tensioner bearing on my 300tdi as it was skriking like fook.. Replaced the original belt and found it to be a little better. Sprayed some WD on the belt and the squealing went and has stayed gone! Now then- i can now hear a tapping noise coming from this area..3 taps, tap, tap, tap- every 5 seconds or so. Whipped the belt off, checked the alternator and waterpump pulleys- seems nice and smooth so am buggered if i know where its coming from! Any ideas?
oh yep- when i checked the belt from the pass side, it seems to be running out of true when the engines going? Tried the penny trick too- did nothing!

Normally a regular tapping sequence is a damaged belt. Had one on my D2 V8. Does the tapping sequence increase with engine speed? If so the it is belt and pulley related I would say.

Thanks Green Hornet- the squeaks dissappeared now altogether. I tried the penny trick again and although not an instant cure (took a day or so of running about) the squeak went. Belts looking a bit frayed now though-which ties in with what you say nicely! will replace at weekend.

Glad I could help a bit