tail lights, sunroof, sunroof drain.
all possibilities

 

Tail light gasket,

Common issue on the 2G

 

 

you dont think a failed gasket can lead to water passing through!??!?!??

 

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NOTE: I've worked on countless cars exhibiting water leak issues. I have never seen a tail light, without some kind of seal, between the light and the body! Very unlikely that your rear seat would get wet, due to a faulty Tail Light seal issue. If, as you say, (" where the top and bottom part of my seats meet are soaked."), I suspect you may have more than one problem. (" I dont even know where to start to diagnose where its coming from.") If my car had this issue, the first thing I would do is remove the rear seat, and all the trim from inside the trunk. Remove all the pooling water, leave the windows down and the deck lid open, and let the car air dry outside in bright sun, if possible. I don't remember, if the trunk light stays on with the headlights off and the trunk open, if so, you may want to remove the bulb. After the interior, and trunk areas are completely dry, get inside the trunk, and close it. Have an assistant with a garden hose, run water, around one tail light first. Have your assistant begin using a very light flow of water at first, slowly increasing the flow, to full force. If, no obvious leak is detected, move to the other tail light. If no leak is detected, direct water to the forward edge of the deck lid, below the rear glass, allowing water to flow all along the "trough", or gutter, that runs around the trunk opening. If no leak is detected in the tail light areas, move on to each rear door. If no leak is detected here, open the sun roof, hop back into the trunk, and have your assistant direct a light flow of water, first at the left sun roof drain, than the right sun roof drain, If you have as much water as you indicate, in both the cabin, and the trunk, the source of the entrance point should be obvious. To insure your sun roof drains are working properly, you can have your assistant pour water in each drain, while you are underneath the rear of the car, observing the rubber hose sun roof drain exit points.

 

tail light gaskets were allowing a little trickle of water in. Put new gaskets on and that problem is solved but still getting water in trunk. Upon further water test i have a bad rear glass seal. Water is getting in and trickling down into the trunk. I want to fix it properly but i have never pulled a windshield or rear window before. I can see water trickling down the wheel well by the sunroof drain. Good thing is its just one side but still. I just cant see point of entry but being the water was concentrated on the rear window its safe to say its the culprit.

 

How much of the rear cabin, and trunk trim, have you removed,, to aid in finding the leak? To confirm, that it's the rear vision glass weather strip seal, you may want to ( Tape Off ) the weather strip. Than re-test it, and see if leak persists. Until you actually identify the source of the leak, you cannot be certain it is fixed! I replaced the front windshield glass in my 85 300CD. If one does this R&R regularly, it's a piece of cake. Even though, I'm modestly handy, mechanically, the next time I need a front, or rear vision glass replaced, I'll be more than happy to pay, to have it done, by someone who knows what their doing!

 

Agree, front/rear Glass can be a real PIA to get right for the DIY'er.

 

The back glass needs to be reset. Pay a professional glass shop to reset the back glass.