I am || close to taking a hack saw to the damned thing.

I've doused it with penetrating oil (like Liquid Wrench), I've turned it both clockwise and counter-clockwise, tearing (2) T-50 sockets in half each way for a total of (4) ruined T-50 sockets.

Is there anything else I can try before I take the whole tensioner off and put the sucker in a vise? I really don't want to end up breaking the head off and being left with a tensioner with a half a bolt threaded inside of it.

Any advice will be greatly appreciated.

Then tensioner pulley bolt is reverse threaded.

I've got an issue with a front idler pulley. I assume the different metals have fused themselves together.

Yep broke a couple T-50 sockets that direction, too. I'm just going to have to get mean with it and hope for the best.

after 225K miles, mine came off no problem

FYI, the SC tensioner bolt on the Series 1 L67 is NOT reverse threaded. Just an FYI so we don't confuse any S1 L67 owners.

You might try PB Blaster. Just curious as to why you have the need to remove the tensioner pulley in the first place ?

I haven't yet. It might come to that. Already doused it with PB. Guess it'* vise and vise-grip time...

Another thing... if you pull it.. put the T50 in it and give it a couple straight on hits with a hammer.

If the threads have bonded inside then this can crack that bonding.

I apologize, I misunderstood your question on my earlier reply.

I have to replace the tensioner pulley because the other one suddenly locked up, and the belt melted half the pulley off in just the time that I could back the car up and park it.

It was strange, it just went with no growling or anything. I assume that the heat that was likely present in that bearing is what is the cause of the bound bolt.

So, I'll just need to pull the tensioner and give it a few good whacks in the center of the bolt, as Bill suggested.