'02 OB belt broke, said she was doing 70.  Pass side exhaust valves are bent.  Belt was 11k miles on it and it looked like someone tried to pull a stump with it.  I was expecting to find a camshaft welded or snapped, both were fine.  What am I missing?

Edited June 28, 20232 yr by opus

Belt.....

Who did the TB change?

Any idler pulleys damaged?  

Something locked up I'd think.

 

Me.  No damage.  Thats what I was thinking too.  I dont know what though.

Is it a 5 speed? If so the Keeper above the crank shaft may have been mis adjusted ( saw this more than once ). If it was other than a Subaru belt, YES I have seen those fail also. Quite a few years ago even Gates went to a Cheap Thinner belt. The original coming off, even worn, felt sturdier than the Gates and others new going on.

 

Had seen about a half dozen with broken belts. Sent heads out for valve replacement, Put back together with Subaru Water pump, pullies and belt and ran for MANY more miles.

Auto.  I have never seen a belt break like this.  Not disagreeing with you though.    Its not like there is a lot of stress on the belt when its rotating.  

If something had locked up. I would think I would notice something on the cog side.  I'll have to take a better look.

Aftermarket belt is most likely culprit. 
 

Use Subaru or OEM supplier onlyfor belt and pulleys

Check rotation of all timing pulleys for grease filled bearings and crank/cam shafts  

Id replace the lower cogged idler at a minimum. 

I've been using these belts/idlers for 15 years without an issue. Just don't see it as a belt failure..... yet.

Going to dig more, we'll see 

I had new one break in a couple thousand miles that was in contact with a lot of oil from a leaking crank seal. Luckily a non interference engine, and it seemed obviously caused by chemical contamination. Though the picture you posted doesn't show any wetness, so I'm guessing it was clean?

You haven't mentioned timing pulleys - were any low on grease or seized?

If nothing else is obvious, Aftermarket parts are like that - it's not like they all fail, but I'd expect 1-3 early failures in 15 years from aftermarket timing belts.

I've seen many aftermarket belts tear apart like that.

Mitusboshi belt, NSK pullies, AISIN tensioner, make sure there aren't any seals leaking oil on it. Have the heads checked. And you'll be back on the road.

What brand is the belt?

OEM or Misuboshi are the only correct answers.

GD