Another pretty big clue will be if your roof is completely rusted over.
I have a leak in my car roof.
If you open it all the way you should be able to see them.
However if you can see any bubbling or cracks in the paint along the sides that s where your leak is.
The drain tube holes are usually located underneath the sunroof itself.
These fixed points can be perpendicular exterior walls a fireplace chimney or other components that extend through the finished ceiling to the attic space or roof surface.
Having a leak in the roof of your car can cause damage when it rains will damage your upholstery as well as trickle water into electrical circuits fortunately repairing roof damage is relatively easy and will save a lot of money in getting it repaired professionally especially if your car is out of warranty.
If you spot any rust near the roof sand it clean it with rubbing alcohol and maybe even use some touch up paint on top.
If there is a leak and the inside of the car smells like coolant a sickeningly sweet smell when it gets warm the heater core may have sprung a leak.
Check to see whether the liquid collecting in the car is antifreeze or water don t taste it.