Tapping noise while idling.

[weav6900]

My 1999 Buick Century(3.1) has started making a clanking,tapping sort of rattle noise.At first I thought it was a loose heat shield,it's that sort of sound.It only makes this noise while idling.Give it some gas and the noise seems to go away completely.Put it in park and the noise almost goes away,except for an occasional irregular rattle.Since I deliver mail in this car I spend a lot of time at idle speeds and the noise is driving me crazy.It doesn't seem to be an internal engine noise,but I can't pinpoint it.Otherwise the car runs great.My mechanic husband is going to put it in the shop this weekend, but I'd like to hear some of your ideas before we start.Thanks for any help.

[GTP Dad]

Check two things, the harmonic balancer on the front of the engine. The rubber insert on these can go bad an cause the noise you hear especially if it sounds like a metal to metal clank. The other possible cause is the belt tensioner. If they go bad they can cause a similar noise in the engine and will make more noise at idle than at speed.

[weav6900]

Just a little closure to this problem.My mechanic went over the car and found a cracked flywheel causing the noise.By this time the car was making an awful racket when starting,so we were pretty sure it was either the flywheel or starter.For now, it's running great!