Originally posted by ChrisGSR
Also, I suppose that if the T/B tensioner really failed hard and froze up, it might cause the engine to skip timing or lose a belt tooth. Ouch! Balance belt tensioner would be a nonfatal failure.
The timing belt tensioner is a smooth faced cylinder that presses against the backside of the belt. You would probably just cause a lot of belt wear if it failed... though obviously if you didn't realize what was wrong or didn't correct it the belt would fail eventually.
I'm staying out of this, as some people advocate changing the tensioners with each belt and others place it into a 'change as needed' catagory.