Fan Belt Replacement

Fan Belt Replacement

From high-end to a stock 36 hp VW engine, knowing how to replace your fan belt is simple and yet critical. It's the cooling life of your air cooled engine. Kudos to our friends, Rob and Dave for the properly articulated information.

To replace a belt, follow the above procedures for the drive belt adjustment, but slip the belt off the crankshaft pulley and remove it.

Note: If you have piece of tinware around the back of the engine pulley you will need to remove it (three screws) to gain access to the engine generator pulley. Don't forget to replace this tinware afterwards - it helps prevent items falling into the valley around the engine pulley.

Remove the bell shaped spacer and the thin shims. Remove the outer half of the pulley, and the fan belt will come off. In-between the pulley halves, will be another group of pulley shims that adjust the belt tension depending on the number of shims used.

Note: You must have at least 10 shims.

Install all 10 shims between the pulley halves as a starting point, and place the belt into position while installing the other half of the pulley. Install the remainder of the shims (if any), then the bell shaped spacer, and tighten the nut down the same way you removed it.

Make sure the key is off, then rotate the engine a full revolution and check the belt tension. You should be able to push the belt in between the two pulleys 5/8". No more, and no less. If you can move the belt more than 5/8", you will need to remove shims from in-between the pulley halves, and add more if you cannot move the belt 5/8".

The belt is tightened by moving the pulley halves close together, which makes the belt ride up higher, and this removes slack.

Remember to rotate the engine between each fitting of shims, to make sure the belt is fully seated before you check it's tightness. Always put any extra shims between the pulley half and the bell shaped spacer for safe keeping for when you need to replace the belt in the future.


  • Eric Shoemaker

    We could not agree more!

  • Rob Caveney

    I had a well known engine builder tell me the fen belt should be “banjo string” tight. I disagreed, and against my better judgement, left it tight. Before long the bearings in the alternator overheated up and it was ruined. Don’t be convinced of something you know is wrong. Go with what you know to be right. The 5/8" test is right. I felt like an idiot for believing him, especially when he never took responsibility for the bad advice.

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