I've had 2 sets of new belts on my 240 GL ( it takes a set of 2 from the alternator to the crackshaft pulley) but I cant keep them tight. They seem to be stretching and get so loose that the alternator won't work anymore. There is no squealing noise however. The locking nut is always tight on the adjuster so it would seem that the belts are just stretching. It doesn't matter how many times I retighten the belts, they get loose again. Anyone else ever have this problem?