Gain access to the attic and with a flashlight find the place where the ceiling is wet between roof joists.
Water leak in garage ceiling.
If you caught it in time you can see water running down the wall and into your garage.
This morning i was in the garage which is below that same bathroom and saw that there was water dripping from the ceiling.
The ceiling is above the bathroom 2 bedrooms a hallway and a hall closet.
Screw type fittings especially in drain traps are more likely to leak than are glue type fittings.
Then i noticed that most of the garage ceiling is streaked with brown water spots and in many areas the ceilng is buckling soft to the touch.
Older roofs may also leak and cause water damage especially during major downpours or storms.
A whole home humidifier or similar water leaking appliances installed in your attic can also cause water damage to the ceiling as well as leaking bathroom failed bathroom waterproofing fridges or other kitchen appliances on higher floors.
If the water is dirty or stains the ceiling the source might be a leak in the roof.
Water leaking into the garage under the wall.
Protect your floor from moisture by laying down towels and old newspapers on them.
This is usually caused by a leak somewhere.
Big buckets will also come in handy for heavy leaks.
A possible cause of a ceiling leak in a two story house is an upper floor bathroom.
In order to solve water leaking into the garage under the wall you have to find the source of.