Ether - Water leaks into both wheel wells but it is more prevalent on the left side. I poured water around the fuel door and it drained on the ground near the axle.
Dadette123 - I run the test on the sunroof as you described and did not see any water in the wheel wells. I saw water exit from the sides.

I saw water dripping from the corners of the area above the vacuum reservoir in the trunk (below the first aid box, on either side of the trunk hinge) after today's rain. I observed rust in these areas upon inspection with a flashlight. I am planning to use some JB stix to seal the area but I am worried that the water is going to stay inside the panel and cause more damage. Can anyone shed light on how water could have collected in this area? Do these areas drain out somewhere? Thanks.

Jazz 84 300D Turbo

Back window seal

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too many w123's
84 280 SL 5 speed

I have exactly the same problem only my leak is on the left side I have done everything except the only possible source is the downslope end of the roof gutter trim. This downward chrome trim is wider and behind this is another plastic grey trim. Behind both these trims are 2 drain holes. I saw pieces of dried twigs or leaves which I was able to remove some with a paper clip and jet water. I just don't know how to remove these trims so I can fully unclog it and water test it. And I also don't know if my guess is correct.

Let's hear from anyone who can confirm this.

Denial is a powerful force. Your leak is caused by a rusted out channel around your rear window. All the sealer in the world applied from the outside will be ineffective. Had identical on my 300CD.

It is fixable (I did) but not inexpensive. Rear window must be removed. I had a windshield pro do it to prevent breakage since the coupe rear windshield is rare and expensive. A good body shop can remove the rust and rebuild the channel. Add a new seal and it is done.

Cost:
R&R rear window approx $100.
Repair rust approx $350 or more depending on extent of damage
New gasket approx $165 for the coupe. Sedan probably much less.

Worth doing if you like the car.

I finally solved the water leak in my trunk by replacing the rear windshield seal $41.99 from Eckler's. The leak stopped! But we forgot to re-install the metal trim molding on the seal before mounting the glass on the car. Too late, no amount of lubrication or soap can help put back the metal trims unless we remove the seal and do it over again. The car looks neat without the trim but it's not the original look. Oh, well, I can live with it as long as the leak has stopped.

There is a small hole, 1/8", under each side of the rear window for draining the seal channel. Look up unto the trunk with the liner removed and you will see them. When my seal was leaking I could feel moisture at those holes. Also the rear seal has a depression at the bottom sides of the window where water can pool up and filter down between the glass and the seal. I sealed my windows with permatex ultra black by masking off the body and the chrome and applying a thick bead with gloved finger. Time intensive but the fix was low cost, and if done neatly and trimmed, will go unnoticed.