About 15 months ago the Toyota dealer replaced the timing belt on my 99 V6 4Runner. About 6 months ago I occasionally began getting a flashing check engine light at highway speed suggesting a random missfire. Gas mileage was also down a bit and idle was a bit rough. The dealer replaced an ignition c…

The dealer probably forgot to torque the harmonic balancer bolt. I would have the bolt re-torqued by a mechanic just to make sure. A loose harmonic balancer can wobble and mess up the crankshaft. For peace of mind let another mechanic torque it again.

One type of damage that can happen if the harmonic balancer bolt is loose is that the HB hub wears and the key and keyways in the HB hub and crankshaft nose wallow out. So the HB and crankshaft should be inspected to see if there is damage to the key and keyways as well as fit of the HB hub to the …

Thanks for the feedback. Apparently under the right conditions, load & rpm, the crankshaft position sensor can interpret a loose HB as a missfire. The Toyota dealer tightend and re-torqued the bolt and said it should now be OK. Not sure that they really checked for damage. Based on your comments, I…

It probably would not make noise or cause roughness until the bolt loosened up again. If there is enough slop to allow the crankshaft to transfer vibration to the bolt instead of the damper, it is possible for the bolt to work its way loose again. So keep an eye on it. Good luck on this.

It turns out that I am now getting a knocking noise when the engine is warm and at idle. It is much less noticable as soon as the rpm is increased above idle. I am wondering if this could be a sign that the harmonic balancer is bad. I did not hear this noise before the dealer tightened the harmonic …

Earlier models have been found to have severely damaged keyways that were apparently caused by stretched timing belts that developed an harmonic slap in the timing belt slack. I suspected that the crankshaft keyway was not properly hardened for such damage to occur. The crankshaft bolt on one truck …

Took the truck back to the stealership today because of the loud rattling noise. Turns out they never removed the harmonic balancer to check for damage after finding the bolt loose. They simply tightened the bolt and told me everything was OK. Today they removed the harmonic balancer and found that …

Good, you kept and eye on the harmonic balance and the bolt. Got it fixed at the first sign of noise. Good work!!

I am somewhat skeptical of the situation, gwb. It would seem advisable to keep all the records on this problem and if the noise reappears any time soon return and ask that the harmonic balancer and the timing belt pulley be pulled for you to inspect the crankshaft keyway.

Loose Harmonic Balancer Bolt

Maintenance/Repairs

ignoramus9 May 7, 2010, 7:03pm 6

an additional point to keep an eye on, is the forward oil seal. I am not sure on the v-6, but on the 22r it rides on the harmonic ballancer and if the HB was loose, it could add to wear or distorion of that seal. A drop of non-hardening lock tight on the retaining bolt would not be a bad idea either when you have it re-torqued.

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Loose Harmonic Balancer Bolt

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