99 Ford Escort timing belt

I have a 99 Ford Escort 2.0. The idler pully broke from the timing belt so we changed it. But it keeps on breaking the bolt that holds the pully to the engine. We have changed it twice and it broke twice. I need some advice on why it keeps on breaking the bolt in half. Thanks

I can think of 3 possibles; It may be a hardware store replacement bolt, & the original bolt might have been a grade 8. Secondly, that is one of the bolts I would use a torque wrench to tighten, following whatever the torque listing was in the tech manual. Lastly, could there be a damaged pulley, like a bent camshaft or water pump pulley, or something jammed in one of the cogs a pulley with teeth? On my 94 1.9 that would be the crankshaft pulley, water pump pulley, and camshaft pulley. ?

Is the bolt actually breaking or is it just coming loose?
I would suspect that it has not been torqued properly, and if the pulley is not seated right then any wobble would work it loose again.

The torque for the tensioner bolt is 15-22 lbs/ft.

I believe the bolt is question is the large one on the crank... correct?

I thought it was the tensioner bolt. The crank pulley torque is 81-96. How could it break off? There's a half moon key on the crankshaft and pulley. Maybe the key isn't there.