If you see a belt that does not have an automatic tensioner and runs between only two or three components, it’s probably a stretch belt. You may also notice some belts will have the word stretchy or stretch written on the back. A stretch belt can last 100,000 miles or more. On a worn belt the cracks or damage to the backing of the belt will not be evident to the naked eye. This is why an inspection method measuring groove depth is recommended. You simply cannot go by mileage recommendations alone.

When inspecting a stretch belt, always measure the depths of the groove with an inspection tool, because the differences between a worn belt and a good belt can’t be seen or felt. The new materials used to manufacture a stretch belt will not crack or separate like older belts before the grooves are worn. Poor pulley alignment is the number one cause of belt noise and premature wear of stretch belts.

If the pulleys have poor alignment, the belt will be worn on the edges and might look frayed. Alignment problems can stem from issue with shaft in play an AC compressor or crank shaft. Alignment problems can also indicate a worn AC clutch or crank shaft pulley dampener that is about to fail. If you are removing an old stretch belt, just cut it, even if the belt is still in excellent shape, the act of pulling the belt over the AC compressor clutch or crank shaft pulley will damage the inner core.

These belts have a thermo elastic core designed to keep tension on the pulleys during a long life cycle. The material acts like shrink tubing for a wiring harness. Once the belt has been run and exposed to the under hood temperatures, the heat will decrease the length of the belt and therefore properly tension it. Never use a screwed driver or other sharp object to install the belt because if the belt is cut or the surface or the grooves of the pulleys are damaged, the belt will eventually fail.

Special tools are available from various tool and belt manufacturers that act as a ramp on the leading edge of the pulley. Some applications will require special tools to, hold the belt on the accessory pulley as is the case for the Subaru AC compressor pulley. There are many tool designs, but they all perform the same task of pulling the belt over the leading edge of the crank shaft pulley without damaging the belt. Always follow the instructions for proper tool placement and for the correct direction to turn the crank shaft after the belt is installed. Confirm the belt is in the grooves and recheck there are no alignment problems. Run the engine for a few seconds before doing this final check.

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This video is sponsored by Continental.