84 300D Turbo trunk water leaks
 

I have been trying to find the source of the water leaks into the trunk wheel wells without succcess. I searched the forum and followed recommendations to clean the drains in the engine compartment and the sunroof but that did not solve the problem. I hosed down the area around the rear window seal with lots of water but the wheel wells remained dry. What I find strange is the water collects in the wheel well even after very light rainfall. I have heard that the flow path of the sunroof drains includes certain areas in the trunk area and was wondering if you folks had any diagrams to share. Where are the actual locations of the drains for the sunroof? I have a feeling there is a drain that I am neglecting to clean. I am planning to use a sealant around the the rear window seal and would like to know if any silicon sealant will do the trick. Any tips and advise would also be helpful. Thanks in advance for your help.
Jazz
1984 300D Turbo

Check the tail light seals, Look for cracks in the tail light lenses and check the trim beneath the tail lights. Also, check the antenna grommet on drivers side and fuel neck grommet on passengers side.

All these places are a source for a leak that puts water in those 2 wells.

Water can also leak from the top of the rear window gasket where it meets the roof.

To eliminate the sunroof completely, open it and pour about a cup of water towards the rear on the side channel one side at a time. Look for water in each respective wheel well.

I forgot to mention it but I hosed down both the antenna and the fuel filler area and found no water in the wheel wells. I will try the other suggestions and report back. Thanks for the responses.

If you hosed down the fuel filler area without plugging up the small overflow hole, you should have noticed water draining on the ground around the axle. As an elimination test, pour a small amount of water in this hole and see if it exits on the ground.

Also, it sometimes helps to not use a hose. Its harder to control where the water goes and to track where the water exits because the surrounding area is wet. Just my two cents. Tracking down a leak is more a process of elimination than anything else. Good luck.

When you check the tail lights be sure to use a flash light, pull the trunk carpet and wheel well liners. It is very difficult to see a leak when it leaks from the tail light gaskets or the tail light trim. This is because it runs down behind the pinch weld and then down under that plastic channel that holds the wire bundle. Then it runs down either side of the bundle and down in to the wheel wells. Also, look closely (with a flashlight) at the "end studs" on the trim beneath the tail lights on each end. There is a small nut and washer that secures the trim. A very small stream of water can run down from there. It is VERY difficult to see if it is leaking from there too.

I forgot to mention above. Don't rule out a bad or leaking trunk seal too.

Good idea. You would think the lip even without the seal would keep water running down the channel. But, if the channel had been rusted through in a spot water could enter the trunk. You'd think it would wet the carpet, though, given its orientation.

Ah, water leaks. There so damn fun to find. :rolleyes:

Dadette123 - When water is poured down the overflow hole it exits on the ground just by the axle. The trunk seal was one of the first things I eliminated.
Snook - I hosed down the tail-lights but did not detect a leak. I doubt that it is in this area because the leak is upstream, around the trunk hinge area.
I put a bead of flowable permatex silicon windshield sealant around the glass area of the rear window seal today to completely eliminate the seal. Thanks for the responses so far.

Jazz 84 300D Turbo

I think the windshield seal has been eliminated as a leak source because I had water in my wheel wells after yesterdays downpour. Any new ideas on why the water gets into just the wheel wells and not the entire trunk. Thanks for the responses so far.

Jazz 84 300D Turbo

Did you do any driving?
Are the covers in place?

toomany MBZ - Yes, I drove the car but I saw the water prior to driving. If you mean the covers on the wheel wells, yes they are in place. Thanks for all your help.

Yeah, those hard plastic covers. The water is not splashing up then.

Did you test the rear sunroof drains to eliminate them?

Is the water in both wheel wells or just on the right side? If just the right it could be a disconnected hose from the fuel overflow drain. Water gets behind the fuel door when it rains and instead of draining out the bottom of the car it ends up in the trunk.

I had this problem in my W116. I assume there is the same drain in the W123 but I don't recall for sure.

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

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.

I agree with Dadette123
 

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.