Tightening Your Belt.


Text - Robert Rawson
An important feature of the Air-cooled VW engine is the belt driven cooling fan, a broken drive belt could cause the engine to seize up - it is therefore very important to keep the drive belt in good condition and at the correct tension. Here's How.

One of the easiest and important adjustments to be made on the air cooled Volkswagen engine as fitted to the Beetle and many van models is the tensioning of the generator drive belt. Because the belt drives both the cooling fan and generator, the belt must be kept in good condition, a worn, damaged or stretched belt must be replaced otherwise belt failure will cause problems, which are expensive to rectify.  

To replace the belt is easy if you use the correct method. (I have seen people try to force the belt on and off with a screwdriver without slackening the top pulley off first, this ruins the belt)

To do the job you will need a few simple tools which are as follows:-

  • A large screwdriver.

  • A 21mm spanner. (A spark plug socket should fit but check first)

  • A new belt if required. (It never hurts to carry a spare)

When referring to the front of the engine I am talking about the flywheel end which is nearest the front of the car and the right side of the engine is on the right side of the car when stood at the rear. Always disconnect the battery before attempting this type of work on your vehicle as some one may try to start the car whilst you are behind it with your fingers in the engine bay.

To change the drive belt first slacken the generator pulley (top one) nut, you will need to stop the pulley from turning by putting your large screw driver in one of the slots in the front (Nearest the engine) half of the pulley and use this to lever against the generator case. Slacken the nut with your 21mm spanner but do not remove it altogether. The pulley halves should separate and allow the belt to drop between them, this should give you enough slack to remove the belt altogether.

Fitting a new belt is the opposite, first put the belt in between the generator pulley halves and then ease it over the lower pulley. If this is too tight remove the generator pulley nut and remove the pulley. This should allow you to fit the belt to the lower pulley first and then refit the generator pulley halves together with the belt in between. Be sure to refit the spacer washers correctly. Tighten the pulley nut being careful not to trap the belt between the pulley halves. Rotate the pulley to allow the belt to seat itself in the correct running position and retighten the nut. If the belt is too tight undo the nut again and put one or two of the spacer washers from under the nut between the pulley halves, if the belt is too loose then take one or two spacer washers from between the pulley halves and store them under the nut. Tighten as before and keep rotating the pulley as you go to make sure the belt doesn't get trapped. To make sure the belt is at the correct tension push the belt at the half way point between the pulleys and take note how far it moves. The correct distance is about 12 - 18mm and should be adjusted accordingly. If you have access to a torque wrench tighten the pulley nut to 40 - 47 lbs/ft. These figures should always be checked in your workshop manual as they can sometimes differ between models and years. Double check the tension by rotating the pulley to locate the belt and check the tension, if it is not right do it over again because this adjustment is important for a long service life of your engine.

Always get expert help if you are in any doubt about your ability, if you are shown for the first time you could do it yourself next time.  

Copyright © 2003-2004 Robert Rawson - All Rights Reserved