I recently had timing belts break - a few days apart - on a 1991 and a 1989. Both were cars that had been parked awhile. I was getting them ready for the road. All that's a whatevs.

Both cars had that common motor noise when warm that I associate with piston slap before the timing belt went; now neither of them have it.

I've had a car with that noise that had a newer belt so I don't offer this as a cause of that noise every time. But perhaps that slapping noise is exacerbated by a weak belt.

One test might be to re-adjust the idler pulley and see if the noise changes.

The general opinion here seems to be that there is no warning on a bad timing belt; and one can't tell a bad belt via a visual inspection.

I won't dispute either of these but I have found that broken belts have visible cracks cross-wise on the inside of the belt. So when I inspect a car with an unknown history I always replace a belt with cracking. On my own cars I replace any belt that doesn't look and feel new.

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240 drivers / parts cars - JH, Ohio