Changing Serpentine or Accesssory Belts

This belts drive connect the main engine rotor to other parts that need the rotational power - like the water pump,Alternator, Power Steering Pump, Air Condition Compressor and the FAN that cools the radiator. It varies from car to car and all cars will have some form of belt driving a bunch of  "accessories". Most of the serpentine-belt installations use a spring-loaded tensioning pulley that maintains a constant load(or tension) on the belt, eliminating the need to adjust the tension. In older cars the position of the alternator can be varied to adjust the tension of the belt. See an example of a an engine showing the serpentive belt driving several pulleys.

These belts wear with ageing and usage and some times will break before the manufacturer said interval. Some times they will last far more than the recommended interval. If there is a squeal coming when you start the car in the morning or lets say when you turn the AC on , it means the belt is going  bad. It could also mean the tensioner going bad. See example of a cracks appearing on the bet with wear and ageing.

Replacement :- In older cars where the alternator pulley is used to adjust the belt , there are mount bolts where the alternator swivels on. Then there is a guide bolt that is used o position the alternator to the correct tension. Once you loosen(not remove) the mount bolt and also loosen the guide bolt the alternator can swivel to a position to free up the belt and you should be able to wriggle the belt out.

For tensioner equipped belts it is almost same procedure abit easier.  Most cars provide a common 3/8-in.-sq hole in the tensioner's arm to release the tensioner. Simply use a ratchet to turn the tensioner to loosen the belt, and wriggle the belt  from the pulleys.

Inspect the belt for damage. Cracks across the ribs are the most common indication of a belt that's simply at the end of its life span. Little rubber bands of rib, tufts of fiberglass reinforcing belt or disintegrating belt edges are indications of a problem with the pulleys, idlers or tensioners.

To put a new belt on , just do the above steps in reverse. For Alternator types , the alternator has to be pushed to the maximum position it can move before you tighten the guide nut. I use a big 'lever' or something like long L shaped wheel spanner to push the Alternator back into position. Once the guide nut is tightened you can tighten the main mount bolts. Check the tension on the belt by pushing the belt , in the middle of the free area between the pulleys. It should be snug and go not more than 1 or 2mm when pushed by a bare hand. For tensioner type some times you may need to de-press the tensioner with a C-Clamp to get it into positon to put its bold back on. Otherwise the procedure is the same.

Note in some cars instead of the alternator , the power steering pump does the job of adjusting the belt tension. So make sure you refer online or  the repair manual.

Start the car now and go for drive to see if there are any sounds and if everything is ok.

All in a all this procedure is a basic DIY in most cars and is a fun project