I had the exact same problem with a 2003 Toyota 4Runner just after we took delivery. The dealer’s service department changed the belt at least 3 times in the first month. One time, the technician didn’t get the belt on correctly and it pulled out the oil seal. At any rate, when we took it back and were most unhappy, the salesman went in on our behalf and talked to the manager of the agency and the service manager. They replaced the belt tensioner and we haven’t had any problems since. This was 4 years ago and we have gone 50,000 miles since that time with no problems. If you don’t get satisfaction from the dealer, you should call the zone representative.