hole on timing belt - how?

[fabster]

Hi all,

I decided to adjust the valves on my 99 EX when I noticed a rubbed line on my timing belt when I removed the top cover. This was already concerning, but when I did my final crank shaft turn for the last cylinder, a hole on my timing belt came into view. My heart dropped. When I look down into the bottom cover I don't see any points of rubbing. I'm assuming the rubbed line might be debris that might be in the bottom cover, but how does a hole happen?

In full disclosure I did my own timing belt two years ago very carefully using the Honda manual and the best videos and guides I could find here and on youtube. I was convinced I had put everything back together without issues. This is really frustrating because the process was really painful and I was relieved I wouldn't have to do it again (the car is at 290k miles). I might just have to get rid of the car at this point but knowing how this might have happened would be a real help. Thanks!

 

[bastok]

Belt tensioner bearing total failure or random failure? (as the damage is on the outside of the belt).

In the picture, I cant see any of the belt teeth....... Maybe as the picture is taken in the side where the teeth are towards the oposite side.

In my civic no matter from which side you look at the belt, you can perfectly see the belt teeth.

 

[bastok]

I can see the teeth in the bottom of the picture.

Looking at the belt damage there must be some rubbing noise. Didn't you hear some strange noise?
By the way, taking the mid cover maybe can be enough to see or figure out where is touching that belt...

 

[fabster]

As an update, there was no noise of rubbing or specific bang that happened, which is partly what baffled me about the scary situation of the belt. The culprit was the bottom left screw from the water pump had come loose and had fallen to the bottom. At some point it must have gotten caught on the gears and punched that hole through it. But looking at the inside of the bottom cover it seems that it just lodged itself into the bottom of the cover and proceeded to rub away at the belt. The teeth were fine, thankfully. You can see on the pictures below that the screw threads are all wasted away from rubbing. I've gone ahead and changed my belt again.

The screw that came off has a position very close to the belt itself where if the belt where I can see that if it was in contact with the head of the screw it could over time unscrew it. Has anyone else ever have this happen?