I just bought a 98 Legacy with a 2.2. It seems to have a new-style tensioner on it, however. I replaced the timing belt because the owner thought it had never been done (120k miles, the mechanic thought it was unnecessary because it isn't an interference engine.. yikes..)
However the belt I found on there doesn't say Subaru on it, and looks pretty good, AND it has the new tensioner on a 98, leading me to think that it has in fact been worked on before.
Anyway, the car had been making loud noises at start that went away after it warmed up. I did the t-belt replacement, but I noticed that the tensioner was slapping up and down- not good, and presumably the source of the noise.
The thread topic is about rebuilding, however- I think I might have made the problem worse, because I foolishly compressed the tensioner piston horizontally. It takes a lot of force to push down, but it pops back up very quickly (too fast?) and it doesn't seem to extend to the 14-15mm that the factory specs I've read call for, although those seemed to be specifically talking about the old-style tensioner.
There is a nice clip that comes off, but tugging on the piston didn't move a thing. There is only marginal oil leakage, and nothing spurted out while I was compressing it, so I think the seals are actually good, and I just let too much air into it. I've heard a new one is nearly $200 at the dealer, and nobody is selling aftermarket units yet. My crazy plan was to inject more oil into the cylinder with a fine syringe in an effort to boost pressure. I've got boxes of very fine syringes (diabetic supplies!) and what looks like an appropriate hydraulic oil. Is this a pointless effort? Can the piston be pulled out and rebuilt with new seals and fresh oil? Should I give up and buy a new tensioner? Is it better to go back to the old-style, assuming it will bolt up properly?