For some reason, I have trouble with the hydraulic door closers. These are
the heavy duty ones used commercially, usually in apartment buildings and
condos. When they no longer close the door the way they are supposed to:
1)a somewhat rapid first closing, 2) a slower closing as the door gets
near the jamb, then 3) with enough power to pull the door into the jamb
and set the latch, I try adjusting them, but with less than 100% success.

Mostly the closer no longer pulls the door into the jamb. I know there are
adjustment screws on them though usually they aren't labeled and since the
closer is old, and I didn't install it, no one has the instructions handy.
Are there rough guidelines for adjusting these so the closer works as it
did when it was new? When closers age, do they break and or leak so that
the adjustments no longer work, or can I adjust the close rate screws and
get them working again? After making an adjustment, I've tried putting the
closer through sereral cycles to make sure, then if I need to, try to
adjust again.

I'm going to try to google for instructions for the ones I'm working on
now, but I'd appreciate some general guidelines.

charles