I've been battling issues with my car the last few weeks since getting it, mainly around electrical stuff. Fast forward to this last week and after another storm my car started acting up. I took the right rear panel off and discovered my SAM was completely soaked and all the connectors, it had pretty much completely messed it up. I checked all the usual suspects with seals doing a ton of water tests and could not locate where it was coming in. I took the SAM apart completely and it had a ton of corrosion on it, I think this car had previously had leak issues. After alot of work and putting it back in place I cleaned it all up and I had no errors and things were good. I thought I had figured out the leak relating to a rear seal on the tailgate which didn't look installed correctly. I had a storm yesterday again and guess what more water! I noticed on my sunroof in the back of it in the middle there is a space about 2mm wide. It doesn't seem like this would be factory, I figured maybe it shrank up over time. I covered this hole with a piece of ducktape, and did a leak test and see no water coming in. I have all the panels disassembled and the headliner partially pulled down trying to see where the water is originating from the channel its going down in the headliner.

I've been trying to do alot of research on this but has anyone else ran into this issue? Previously I had a sunroof seal on my BMW which resulted in my backseat getting flooded! I'm trying to figure out exactly whats the deal with the sunroof drains, theres so little space in the back of the sunroof, I can't even see where they are or how to even service them. Even with a slight hole in the seal they should be draining with the drains right? Perhaps one of the drains is disconnected? I may try to see if I can remove the door hanels on the right side and see if I can shine some light to access any of the drains. Its been a nightmare so far. If anyone has any insights or tips it would be appreciated.

 

@esphil Check the moonroof drains. You can pour a small amount of water into the drain trough and see if it comes out under the vehicle. Search this site, google and youtube. You will find the information.

Please post a photo of the 2mm gap.

 

Thanks for the quick reply. The front are perfectly fine but I can't really see the back drains from in the sunroof. I filled in the gap already with some gasket sealer, I let it dry overnight and I'm going to add a bit more today. I was previously using a hose for the test, maybe thats alot of pressure. I'm going to try to pour a small cup of water later. Regardless of the gap I expect they should be draining. I've seen alot of videos about the drains but not too much information on the location for the w164 rear drain. Its just so tight in the opening with the cover and when you raise the roof. I almost have to use a camera to look better.

 

Update, I found the issue! Its actually the white box that is in the back of the sunroof that connects to the roof that has a leak in it! I filmed a video I'll be putting on youtube for people who run into this issue. Theres really not much information or people who have really had that happen before. Hopefully it helps some.

 

@esphil Well done! Looking forward to the video.

 

I posted up the video, I should have filmed it horizontally, oh well. Hopefully it can help some. I put on some silicon and I'm waiting for it to dry before testing it out.

 

Thanks for posting!

 

Esphil,

Great work hunting down this leak (kudos to you to taking half of your headliner off...no small task)! I too have been plagued by water damage to the rear SAM unit and figured I'd share my experience here to try to consolidate the solutions surrounding this water ingress issue. During significant rain events I would always get water in and around the SAM unit with significant pooling of water directly on the top of the SAM connectors as well as on the metal mounting bracket:


(picture of water ingress with SAM unit removed)

After browsing this forum for many months I have tried all of the suggested solutions that are out there. I have gone through properly replaced the seals around the tail light housings with the updated thicker seals and water was still getting in. I have checked all of the sunroof drains and none leaked water into the vehicle. I sprayed all rear window seals with a high pressure hose, no leaking from there. I sprayed the perimeter seal of tailgate with a fine water stream and still no leaking there. I tried as best I could to spray up from the underside of the vehicle into the rear quarter panel area and could not get any water into the rear SAM area.

Today I finally took the time to systematically go through every single seal in the rear half of the vehicle (starting from bottom of the tail gate gasket and working my way up to the seals around the sunroof) to see if I could isolate the leaking seal. After about an hour I found that the accordion style rubber boot on the lift gate hinge was leaking on the bottom side of the boot where it mates up with the plastic body shroud!


The rubber itself was completely in tact and visually looked OK, but when I pulled back the rubber boot I saw that the hard plastic snap feature that it was installed onto was totally destroyed! This broken piece was allowing water to pool up on the bottom side of the boot, weep through this cracked mounting connector, and subsequently run down the wire loom located inside of the D pillar and drip directly onto the rear SAM.


When I poured water directly into this hole, the resulting water that pooled inside of the rear quarter panel was an exact match (in both pooling location as well as splash pattern) to the water ingress that I would experience during rain events. I have since sealed up the perimeter of the seal with weather stripping adhesive, and so far I have not been able to get water past it! I will continue to keep my SAM out of the quarter panel for the next few weeks just to be on the safe side and monitor for any signs of water ingress, but fingers crossed this is the solution to my problem! I just wanted to share this information here so it can be a "one stop shop" for locating leaks that can (and do) damage the rear SAM units.

Best,
Joe

 

Nice find there! I'm realizing that you really have to stay on top of these cars with potential issues. Its crazy to me how many different areas water can pool in. When I was originally trying to find my problem I was looking at that exact area to see if water was coming in from there. I was also looking at replacing seals around the tailgate, and I discovered alot of these parts are actually really difficult to find. Whats crazy to me is I don't even know how you can service the sunroof drains without even taking off the headliner. In addition to my previous video I discovered more things. I didn't initially realize the top of the water box with the drain is completely open on top by design. Feeling up into there it was filled with leaves! I removed all of those, and managed to rig up some air, and I blew some air down the line with minimal pressure. I also fixed a hose to a small tube and pushed some water down there, it finally looked like it was starting to drain. In addition to all of that the hose itself had a very small leak at the bottom and I had to seal another part of the box, it seems like the entire edge has a leak. On many other cars I've had I can easily service the drains in the back, but not on this car. I tested hitting the sunroof with water, so now it doesn't appear to have any water entering the channel in the sunroof. The leaks mentioned are from pouring a whole cup of water directly into the channel. At this point I'm continuing to use silicion to seal, and I'm siliconing the entire edge of the pipe going into the drain, so I don't have to mess with it anymore.

 

Posted a followup video.

 

Was it hard to get the liner down? Any help on how to? i think i will be checking mine before the winter, Thanks

 

Theres a youtube video removing the entire headliner for the w164. I didn't want to have to remove the entire headliner though. What I did was remove the side panels around the glass on each side. Then you can undo the clips and remove the rear handle. You can pull down slightly from where the rear handle is, there may be a clip on the roof in front of that. It should give you access to the drains. I was very suprised to find both of mine completely full. I don't even know how you get that many leaves in there unless the previous owner left the sunroof open all the time. I had some torrential rain the last week for a number of days which really gave the car a test. Since my fix I have had no water enter in the cabin or show near the SAM, so I'm pretty happy about that. I would inspect the sunroof seal to see if there is any gap at all, I suspect maybe the Texas sun shrank the original seal and left the gap.

 

Will check mine next week, i got to take it off to track a short somewhere in wires going from a rear SAM to where rear tailgate opener is on top on rear right. should be fun.