Recently purchased a used 2016 Pilot. After a rain (Pilot has a sunroof) when I open the rear hatch door water comes running out of the hatch door and into the back of the Pilot. Have taken it to a Honda dealer and they could not find a problem but when they tested it with pouring water on roof and opened the rear hatch door water came pouring out of the sides of the door. How can this problem be solved?
Look carefully along the whole path the water takes from the top of the roof into the recessed area, then along the top of the door and down the sides. There may be something blocking the flow, like a dislodged gasket, or there may be small drain holes that are plugged up.
Most common reason for this is clogged drain holes for the sunroof. You can test by opening the sunroof and pouring water onto the exposed area of the body. The water should drain under the car. If not, you have a clogged sunroof drain.
Also check the inside of the hatch at the top and the sides. Debris (leaves, twigs, etc) builds up in those spots in my 2006 Sienna and if it isn’t cleaned out regularly the hatch leaks into the cargo area.
I am surprised a dealer was stumped by a non-draining door/hatch…Look at the bottom of the hatch door itself. There are likely to be small holes along the bottom edge, toward the outside edge. Get some weed whacker plastic line or something similar and poke up into those drain holes. Something is blocking them from draining properly. If they seem clear, the inside trim panel may need to be removed to spot the blockage…