Interior leak - VW 2003, 1.8 20V Turbo

I recently purchased a 2008 BT50 dual cab then 2 days later we had 500mm of rain and of course it leaked :( I had about 80mm of water on the drivers side floor and 30mm on the passenger side floor. I stripped the interior out of the car and started hosing the outside and watching where it was coming in. I took all the windscreen surrounds off and the cowl panel off below the screen there was no water coming in from that area. I had taken the gutter seals off but left the door seals on so the water was running down around the outside of the seals (with the door shut) and out at the bottom. From inside near the drivers side kick panel I could see water coming through seams in the metal work and when I took the door seal rubber off the body on the car I could see water was getting in at the top of the door seal rubber going down the front inside edge of the rubber and getting in through the seam where the rubber push's onto the body of the car (first problem). I took all the door seal rubbers off and run a bead of non corrosive silicon inside the cavity and pushed them back on. It seemed to have fixed the problem I dried the carpet and put it back together..Two weeks later we got another 325mm of rain and it leaked again :( not near as bad this time. Looking at the bottom of the door where the door trim meets the door I could see water coming from behind the trim and then into the car. I took the door trims off and could see water gets in when the window is up (all cars do) and is supposed to run out the drain holes in the bottom of the door but the water was dripping and splashing up to the back side of the door trim against the sheet of plastic that is supposed to seal against the door with the black mastic (it doesn't) and running straight into the car. I cut some plastic and siliconed them onto each opening on the inside of the door frame and then put the factory piece of plastic on as well (properley this time) as a backup.
So far so good.

1 of 2 places.
1. The windshield on the driver's side towards the lower corner. This is the more common location, and causes water to run down the a-pillar, and drip on the cab fuse panel / GEM

2. The less common location, power roof panel. Some times this will have an issue and water will run down the a pillar, similar to the leaking windhsield.

have you checked to make sure its not leaking into your oil. most heater core leaks will be on the front floor of the passenger side of the car.

sounds like your turbo return pressure line may be leaking i have seen it rot near the hold down bracketby the oil filter housing on the driver side of the engine in the front so i bet thats your issue

where your battery sits look inside there maybe some twigs and leaves blooking the drainage holes look all along there i had similar problem on vw passat no arm in looking hope this helps?good luck

I had a VW rabbit that developed mad electrical problems. It started when one day the headlights remained on and would not shut off. It turned out that a $2.00 gasket for the antenna wire had failed. This allowed road water from the wheel well to leak onto the fuse box. In time the fuse panel corroded and shorted out. I had to replace the fuse box twice and use rubber epoxy to seal the leak.
Check all fuses and electrical wiring for signs of shorts or corrosion.

on the passenger side floor??
it is one of two things
1 drain tube for air conditioner is plugged up is an easy fix find the tube on the right hand side firewall and blow into the tube with an air compressor to clear the tube
or the heater core is leaking

Most likely a leaky gasket. The water pump is a likely candidate, but also could be from a bad radiator hose/thermostat connection. Would suggest washing down the engine with a hose connected to the hot water. While the engine is cold use the hose to wash off the oil & grease deposits and old antifreeze. Allow the engine to dry without running the car. Once dry start the car and be prepared to look for the first sign of a leak. Sounds like a dealer issue since there is very little work clearence between the front of the engine and the car body. Barely enough room to be able to change the serpentine belt.

several possabilities , first ned to preasure test cooling system to find if it has a leak or if it was just overheating and purging coolant. another strong chance is the water pump

check out your door seals may need replacing. drive it thru a carwash to locate the spot.