Is it leaking between the tensioner and the block or between the small hex and big hex? If it's between the tensioner and block, replace the crush washer. You should prime the tensioner whenever you remove it. Dip it in oil springy side down with oil above the level of the crush washer. Pump it slowly 10 times then install.

If it's leaking between the small hex and big hex, it's probably best to get a new tensioner.

Sixto
93 300SD 3.0