Checking and fixing belt tension

After I changed the alternator belt some time back, a squeal had redeveloped.

This was likely due to the tension backing off after it had worn in, so a short while ago, I tried to fix it by tightening it further, but unfortunately, guessing the tension was a hit and miss effort.

I got it to a point where there was a squeal for a few minutes at start up, and this would disappear during driving, so stuck with that.

The support bolt for the alternator also had sheered edges on it, so I got a replacement over the weekend.

Today, I got it up on the ramps, got two thin pieces of timber, placed one across the belt, supported on the pulleys, making sure there were no sharp edges to damage the belt of course.

Then, I took the second piece with it’s smooth edge, and pushed against the belt until it wasn’t moving – this was intersected with the piece I had running across the belt, so that I could see how far the belt would deflect with the small piece pushing against the belt.

Then, I carefully held both pieces together, and got a ruler and measured the spot – it was at 16mm – therefore too loose.

So I tried tightening it as I did previously, by trying to pull the alternator down whilst tightening the bolt – but this would only give me 15 – 16mm.

The workshop manual for my Hyundai 1997 Sonata found free (after registering) here. This stated 6mm deflection for new belts, and 12mm for older belts, with adjustment required after a new belt has worn in.

I removed the air intake assembly, this allowed my partner to push some force from above down on it, whilst I tightened up the bolt underneath.

I then checked tension – 12mm! Perfect.

Put the air intake assembly back on, made sure both bolts were tight, and then started up – sweet, silence, no squeal perfect.

Took it for a run up the street (incase it squealed under load) – no squeal!

Perfect! Very happy with the result, I should have got the ruler and timber pieces out sooner.

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