My 97 Caravan (110,000 miles) chirps. The belt chirps and sometimes under load it will squeal. The belt looks fine, so I replaced both idler pulleys, thinking it could be a bearing. That did not fix it. I then pulled the alternator out of my Intrepid installed it into my van, that did not fix it. I then put a new belt tensioner on, that did not fix it. I replaced the belt, that solved the problem for a couple of months, the noise is back, and that did not fix it. When the engine is cold the belt does not make the noise, but when it warms up it make the noise. I put the old belt back on and while the engine was idling I spayed the belt with a little WD-40, that would quit the noise for a few seconds and then it would come back again. I am not sure where to look now. Any suggestions would be appreciated.