Wet basement ceiling

[I'mTeachable]

A couple days ago I noticed water discoloration on the garage plaster ceiling under the shower stall. The house was built about 1972. The next morning, before investigating, I took a quick shower. Then popped off cover, cleaned out goopy putty between flange and black pipe, cleaned out pipe with vinegar, then Scrubbing Bubbles using a long bottle type brush. At the suggestion of local hardware store person, quickly poured 2-3 gal of water down pipe which drained down very quickly. He said PVC never cracks, so it must be a leaking pipe with water flowing to the lowest point which would be under the shower stall. Took faucet, flange etc off and could detect no moisture on the copper pipes in that area. In the meantime, my garage ceiling has huge water stains that seemed to be between the joists and since yesterday have joined and spread to cover nearly a third of the ceiling. (I have dig pictures). I don't know if the water is from my quick shower, the 2-3 gal of poured water, or jiggling the pipes being the wall.
Since then the black pipe (abs?) going down from the shower has completely dried. Looking at it straight down, there appears to be a crack (a white line across the black pipe) about 9 1/2 inches directly down just before it curves away. I didn't see it before, but maybe the pipe wasn't dry enough. I could take a picture if that would help. The shower stall is a single inserted unit.
Could you please explain what is happening and what to do about it?
I've googled and ask.comed for hours without finding much pertaining to this. Your site seems to have the most intelligent and comprehensive answers. I hope you can help me.

[HayZee518]

drain lines back around your house era did use ABS plastic. The cement they used was black with a plastic particulate matter in with the cement. The joints didn't make up as snugly as the white pvc and fittings. The joints were essentially a slip fit with no taper in the fitting. White pvc does. ABS plastic flexes a little but does and can crack. I'm afraid you ARE looking at a crack in your effluent line. I can't guarantee it but you could try some ABS cement with suspended solids in it to coat the crack. fasten the dauber to a long stick and try to cover the crack. best solution would be to replace the broken section.

[I'mTeachable]

Thank you. I forgot to mention that I detected sewer odor from that area for a couple days before discovering the wet ceiling. Can't remember what diagnostic significance that had.
You are suggesting that I cut a hole in the ceiling above the drain pipe, cut away the piece with the leak, find an abs piece of the same shape (it curves away from sight). How would I join these ends? Since its no longer in common use, is abs piping easily available? I didn't see any in our local hardware store which is very well supplied with plumbing stuff.
If it works, how long do you think the ABS cement with solids would hold up?

[HayZee518]

if you can gain access to the pipe another thought came to mind. perhaps a fernco rubber coupling might be an easier way out. its flexible enough you can squish it into place then slide it over the cut ends which I hope isn't too far away from each other. if your splice is a foot long, two fernco couplings and a piece of pvc pipe will repair it.

[I'mTeachable]

sounds like a plan. No place I've called carries ABS pipe or cement.
Guess it's time to get up courage, get the sheet rock saw and make a hole in the ceiling. Since it's an effluent pipe, is there a reason to turn off the water?
Do you have any idea what cause the crack? And should I can anticipate a similar problem with the rest of the abs piping in the house?

[I'mTeachable]

Violin, I'm confused. If I find that the leak is at the copper pan drain area, how would I fix it?
What about what seems to be a crack in the ABS 9 1/2 inches down?
I haven't personally checked Home Depot, but have been told the old ABS size and fittings don't match the current ones.
And are you suggesting I follow the pipe to the ground and install an expansion/contraction joint?
Forgive my inexperience, but could you please clarify these points. Thank you.

[Redwood]

Before we get all crazy why not open the ceiling and have a look see at where it's leaking.