Check your windshield gasket. It is probably old and cracking. My car had the same problem, I went to Autozone and bought some black silicon, and ran a bead along the bottom corners where the glass meets the gasket. I also put some between the gasket and the roof. You should be able to put your fingernail under the gasket and carefully lift it enough to squirt some silicon between the paint and the gasket. After that, no more wet carpets. To find the drain holes, open the hood and look in the areas that the hood springs are. Hope this helps.
'82 300D Turbo 216k miles