M11 Plus Series Engines Operation and Maintenance Manual – 013-021   Belt Tensioner, Automatic (Alternator)

Belt drive systems equipped with an automatic belt tensioner can not be adjusted. A belt tension gauge will not give an accurate measure of the belt tension. The automatic belt tensioner is designed to maintain proper belt tension over the life of the belt. Only an inspection of the tensioner is required.

The belt tensioner is designed to operate within the limit of arm movement provided by the cast stops when the belt length and geometry are correct. If the tensioner is hitting either of the limits during operation, check the mounting brackets and the belt length. Loose brackets, bracket failure, alternator movement, incorrect belt length, or belt failure can cause the tensioner to hit the limits.

Use a 3/8-inch drive breaker bar to hold back the tensioner and relieve the belt tension.

Rotate the tensioner away from the belt until it stops.

Remove the alternator belt while holding the tensioner back.

Remove the belt tensioner from the engine.

Install the tensioner with an M10-1.50 x 70 capscrew. Align the cast locater pin on the tensioner with the hole in the bracket before tightening the capscrew.

Install the alternator belt over the pulleys while holding the tensioner back with a 3/8-inch drive breaker bar. Use care not to damage the belt while working it over the flanged pulleys.

Release the tensioner, and remove the breaker bar.

The belt tensioner is designed to operate well within the limit of arm movement, provided by the cast stops, when the belt length and geometry are correct.