4 months ago my 2002 outback had a head gasket leak fixed,new clutch and timing belt replaced.Last week the car broke down and the bolt holding the pulley for timing belt sheared resulting in major damage.What could cause this to happen? JOE
Only thing I can think of is over tightening the bolt…although that bolt is usually pretty damn big and is torqued down to over 80lbs.
“What could cause this to happen? JOE”
The overall poor design of the modern Subaru engine.
There are at least six pulleys (maybe more) on this engine that come in contact with the timing belt. Without knowing which pulley you are talking about it’s impossible to speculate on the cause.
Some of the pulleys are not always removed during the timing belt replacement, others HAVE to come off. A bolt improperly torqued during installation could have broken, or it could have been a bolt that was never touched.
The older 2.2 liter Subaru engine is not an interference design, and would have survived this failure with minimal damage.
Have you seen the pulley the bolt was attached to?
If the car has high mileage it’s possible that the bearing could have seized and the new belt had enough bite that it twisted the bolt off when the bearing locked up.
This is also why the tensioner pulleys should be replaced if the vehicle has higher mileage; say 100k or better.