Apparently the timing belt tensioners from subaru are 100% hydraulic, and are quite prone to issues, not coming up to tension quickly enough, and generally being unreliable. I know mine is about to have the 6th Subaru timing belt tensioner put in in its 110k mile lifetime because a brand new one put in about 10,000 miles ago turns out to be defective. Apparently it's the root cause of my periodic missing on acceleration problem I've had ever since that preventive maintenance.
Lack of tension on the initial startup after the job is likely to blame for the belt jumping a tooth, damaging the belt, and intermittently allow the timing off just enough to be an intermittent pain in both my and my tech's ass.
Apparently, as the story further unfolds, not only is there a TSB on the issue (which was followed to the letter on the actual replacement of the belt), but upon the re-replacement of the belt, and manually turning the engine 10 times (vs the prescribed 3) this thing still hadn't come up to tension. As the story further unfolds, we learned that aftermarket tensioners apparently include a spring as a backup to the hydraulic tensioning, and once it's pumped up to tension it wont' recede the way a Subaru tensioner would. Subaru relies only on the hydraulic action to tension, and has no backup.
So yet again (in addition to the stories of aftermarket head gaskets being superior to OEM sube), we have a story suggesting strongly that aftermarket parts makers have done what you'd expect expensive OEM parts to have done -- fix design flaws.
Anyone with experience have data points confirming or denying this?
Best Regards,
-- Todd H.
2001 Legacy Outback Wagon, 2.5L H-4 Chicago, Illinois USA