Drive Belt Check,
Adjustment and Replacement

This article covers the following topics -

1. The alternator/generator drivebelt, also referred to as a V-belt or simply fan belt, is located at the rear of the engine. Because this belt drives both the alternator and the engine cooling fan, the good condition and proper adjustment of the belt are critical to the operation of the engine. Because of their composition and the high stresses to which they are subjected, drivebelts stretch and deteriorate as they get older. They must therefore be periodically inspected.
2. With the engine off, open the rear hood and locate the drivebelt at the rear of the engine. Check the belt for separation of the adhesive rubber on both sides of the core, core separation from the belt side, and/or severed core.
3. Also check for fraying and glazing, which gives the belt a shiny appearance. Both sides of the belt should be inspected, which means you will have to twist the belt to check the underside Use your fingers to feel the belt where you can't see it. If any of the above conditions are evident, replace the belt.
4. To check the belt tension, with your thumb push in on the belt midway between the pulleys and measure the deflection with a ruler. The drivebelt deflection should be about 1/2-inch. If the tension is more or less than this, it must be adjusted to bring the tension into specification.

1. To adjust the belt tension, you must first remove the pulley nut. The front half of the alternator pulley (front is front) has some cut-out slots in it. Insert your big screw driver into one of these slots to hold the pulley stationary while using your 19mm wrench to loosen the pulley retaining nut.

Note: VW supplied a tube spanner with every car just for this job (it also fits the wheel nuts and spark plugs!), but any 19mm box wrench (ring spanner) will do the job.

2. Remove the pulley nut, and you see a metal bell-looking thing, and under that are some shims. Remove all that stuff and then remove the rear (rear is rear) pulley half.
3. Belt tension is adjusted by inserting or removing shims between the pulley halves.

Note: Although the shims are thin, removing or adding even one makes a considerable difference in belt tension.

Note: Spare shims are placed just underneath the metal bell, so the complete stack of shims and pulley halves remains the same. This ensures that the nut will fit the shaft correctly, and the spare shims will be available for future use.

Note: When removing the shim stack to replace the belt with a new one, it's a good idea to keep the the shims between the pulleys in a separate stack to the spares, so you have a starting point for the number of shims needed for the new belt. Most often, a new belt will require more shims between the pulley halves.

4. Install the belt, shims as needed, the outer pulley half, spare shims, bell-shaped washer, and retaining nut. Make sure that the fat bell-shaped pressure washer is in place immediately under the retaining nut. This washer is essential in maintaining an even pressure around the pulley hub through the shim stack.
5. Stop the pulley from turning with the large screwdriver as described above and tighten the nut securely.

Note: You may find it useful with a stiff new belt to remove the locking screw driver and keep tightening the pulley nut so the engine turns over a few times. This will help the belt climb out of the valley between the pulley halves as they tighten. Replace the locking screw driver in the slot for the final tightening.

6. Recheck the belt tension and repeat until the drivebelt tension is correct.

Note: The problem with this adjustment method is that you have to guess how many shims you need to add or subtract, then put it all back together and check it. If it's still not correct, then you have to go back and do it again. This is not the best design, but it works.

1. To replace a belt, follow the above procedures for the drivebelt adjustment, but slip the belt off the crankshaft pulley and remove it. You will need to remove the piece of tinware around the back of the engine pulley (three screws) to gain access to the engine pulley. Don't forget to replace this tinware afterwards - it helps prevent items falling into the valley around the engine pulley. Nothing cuts up a new belt faster than that missing screw!
2. Start the engine and make sure the belt is running true. Turn the engine off and recheck the tension - about 1/2 inch. If it's OK, you've finished the job.