1999 Legacy Brighton Wagon EJ22 engine, replaced failed timing belt

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Joined: 01/27/2012
1999 Legacy Brighton Wagon EJ22 engine, replaced failed timing belt

Hello all, I bought this used, a 10 year old fleet vehicle with ~73K miles. It now has 123K.

Recently one of the timing belt idlers (the one nearest the water pump) chewed itself up and caused a belt failure.

My daughter had just gotten back from borrowning it and told me "it was hard to start".  I started it, and when I heard that can of rocks sound, I turned it off. 15 minutes later I tried to start it without success.  

The belt is not original, judging from the new/clean look of it, and the generally grimy timing belt enclosure.. So I'm guessing someone replaced the belt (perhaps right before I bought it)  but didn't replace the idlers as Subaru recommends.

I got a NAPA timing belt kit, BNH-2523040 and did a careful disassemble, clean, inspect, replace. It was a gamble, since everything I can find online tells me my EJ22 engine  (2.2L)  is an interference engine. 

But the belt basically failed while the car was idling in the driveway, and short of pulling heads to visually inspect valves and pistons, I couldn't come up with a way to rule out interference damage. 

And I noticed in the instruction sheet included in the kit, 1999-2008 EJ22 *Legacy 2.2L* (and others) the instructions say 

"Caution: This engine has been identified as a FREWHEELING engine in which the possibility of valve-to-piston damage in the event of a timing belt failure may be minimal or very unlikely..."

Well the good news is the engine started right up and seems to be undamaged. I've been driving it short trips around the neighborhood, and a few minutes at highway speed. Seems like my trusty Subaru is back in service.

And so the question remains in my mind: was I lucky to have bought a non-interference Subaru?

Or lucky in that it IS an interference engine, but only at high temp/high RPM/high engine wear conditions...mine failed while idling in the driveway.

Or, was I lucky that my 1999 Subaru has an engine made in the tail end of the previous year? (How could I tell?)

I can tell you it has the hydraulic belt tensioner with the tensioning idler attached to it, which is ?newer? than the setup my service manual shows (which is tensioner pulley eccentric-mounted, separate "deadbolt" hydraulic tensioner)

I thought 1997 was the last non interference EJ22 engine, 98 and newer were all interference.

OK, so how do I VERIFY if MY PARTICULAR ENGINE is interference or non-interference? Is it up to me to mike out part dimensions, clearances, deck heights or whatever and do the math? I hope someone can point me to an easier method, or information source.

Thanks for your time and attention.