Since I own my 98 ITR never drove the car on the rain until yesterday and found my trunk full of water. well I did DIY on how to fix this problem. not a expert but I hope you get the idea and it works for you
Main reason, tail light gasket goes bad or the actual gasket around trunk !
1. Tools- Black waterproof silicone, 8mm Wrench, paper towel, degreaser, new tail light gaskets.
2. remove black panel behind tail lights couple push in clips
3. remove the 6 8mm nuts. DONT LOOSE THEM !!! and be careful with your hands when taking last two... use gloves if possible.
4. Unplug the square harness the rest comes out with tail light
5. remove tail light
6. remove gasket from tail light
see the how worn out is the old gasket this is no bueno !!!
7. No look at your tail light closely there’s a gap where water runs down and thru time the gasket in there goes bad and water leaks inside. so we are going to place a strip of black silicone around the tail light to prevent this.
8. after you finish both tail lights go back to the car and you would see how dirty is the area where the tail light goes and if you pay attention you will see where the water runs into the turnk. Clean this up really good with your degreaser and dry it. ad a strip of silicone around the hole area where the tail light goes into place.
9. Last step put everything back on the same way your remove it and enjoy your dry trunk !