I've had small amounts of water show up in my spare tire area once in a while, and from some searching on this forum most people are mentioning a clogged sunroof drain that may cause this problem. I was unable to locate this sunroof drain hose or find any debris in the sunroof rails that could possibly cause a drainage problem on my vehicle. Even checking after a good rainfall or after going through a car wash, I couldn’t find any water or how it was getting in.

my next suspicion was the tank under the spare tire (I think its a compression tank for the airmatic suspension but I’m not sure). I’ve felt moisture on it before and thought maybe due to all the heat waves we’ve had this past summer it was just a lot of condensation that was building up and causing the water. ended up wrapping the tank in a chamois and leaving it for a bit, came back maybe a month or 2 later to again a little bit of water in the spare tire area but the chamois around the tank completely dry.

I’ve seen people recommending sprinkling some flour or powder around to then find trails of water to locate the source, but I didn’t want to muck around with flour or powders. Ended up laying down some shop towels in places I suspected could be sources and then taping them down. Came back in 2 weeks after some driving in wet slushy weather and finally located what I think is the source of water. looks to be coming from 2 holes that should technically be properly welded and not allow water through (the weld is probably deeper in the hole and not what you can see from the spare tire area). they look to be just behind the rear tires so water must be kicked up from driving and slowly penetrating through a tiny hole in the weld.

I’m letting the vehicle dry out a bit before I apply some grease in the hole and then also seal the hole from inside the spare tire area.

photo below of the spare tire area and my shop towels pulled off and laid out to see which ones are wet. The red circled areas are the 2 holes that the wet shop towels were shoved into and where the water is coming from (hopefully only these spots).

I've learned a lot on this forum and hope this helps someone out!

 

I'll check mine when we get back up to Montreal, but I removed the spare and have a big-a$$ portable booster/power pack in its original cardboard box. I charge it up every few months or so and have never seen any sign of humidity.

Princess sleeps indoors, so less susceptible to dirt/vegetation getting into/clogging the sunroof drain(s). I've never looked for the drains, but there are usually at least two in the corners of the sunroof and not always obvious. Sister had this issue with her Tiguan, brother-in-law with his Rabbit. Both sleep outside. Both had clogged drains, both were unblocked by sticking a 14" tie-wrap into the opening and turning it repeatedly. Worked on both vehicles.

Good luck and post back with your results

 

If I am able to locate the entry point from the outside, the better. Sealing from the inside will prevent water from coming in , but there will be water retention on the other side which may lead to rust around the area .

Just something to consider. Not an expert in sealing these vehicles

 

i completely agree. i attempted to find the source from the outside but was unable to. I had my wife pour some water down the hole using a straw from inside the spare tire area while i was under the car looking for where it was coming out...no water ever came out . Ended up putting around 8 straws worth of water on both sides and nothing. i even managed to shove a skinny short red wire into the hole and then I tried using a borescope camera to find the red wire. i tried from outside under the rear of the car, and even tried from inside by removing some of the rubber seals in the bottom of the spare tire area, i was never able to find the red wire. Mind you it was hard maneuvering the camera in those tight areas, but i know i was in the vicinity of the red wire for sure and should’ve been able to see it.

What i did see poking around under the spare tire area from the inside was the Def tank and also some other shielding or panels down there. everything looked a bit dirty and had white residue, i assume crud from road salt. My assumption is that while that bottom is generally open to the outside/not sealed off it is fairly protected by some panels and not meant to have direct impact from road debris. Def tank and plastic shields on the passenger side and then exhaust and heat shields on driver side plus whatever else i didn’t see. The little bit of water that we poured in is probably resting on a panel now and will slide off once i start driving.


I've let the car sit outside in the rain, gone through a car wash, and also gone out highway driving in the rain and inspected that spare tire area after and had it be completely dry. Then randomly i check it and there is a bit of water in there. My guess is it has to be just the right amount and force of water to be able to defy gravity and make it up that hole into the spare tire area. Very likely while driving through big puddles fast and water is shot up there. I think it also has to be coming from the right direction. from me poking around, the hole isnt actually open downward, it looks to have a small opening that goes towards the front of the vehicle. To find the hole on the outside i might’ve had to be approaching it more from the mid of the vehicle looking towards the rear vs trying from the rear or under by the rear tire.

For now i sealed it off, shoving as much sealant as i could to fill the hole through to the outside and prevent water from pooling anywhere. I’ll check it again in a few weeks or months.

Hoping i solved the random water appearing in my spare tire area.

 

I' on my 3rd ML, now a 2014 350 Bluetec. I did have the issue with previous cars of water penetrating the taii light on the right hand side and damaging the SAM computer. a dumb place to put electronics if you ask me. It took 2 SAMS and several attempts for my mechanics to seal the tail light properly. My current car, the 2014 ML 350, I've only had for 2 months before I discovered about 3 cm of water in the left hand tail light cavity. So I took it to the Mercedes dealer and they supposedly water tested everything i.e., roof and taillights, body panels etc., and identified the leak source as the tail light gaskets which they replaced at a cost of about AU$660 for parts & labour. Two weeks later we had heavy rain and again the left hand tail light cavity was full of water. I also found water marks inside the car at the rear left hand door pillar, directly underneath where the middle support for the cargo rails is fixed to the roof. So I took the car back to the dealer and showed them the water marks (see attached pics) and suggest the roof cargo rail connection may be the issue. Anyway they rang to say the car was water tested again and the leak identified as being caused by a blocked sunroof drain hose which is very odd because the previous invoice stated that they had cleaned and inspected the sunroof area and drain. Also if that was the source of the leak, then they should have identified that when they water tested that same area two weeks earlier. Anyway when I picked the car up it was obvious the mechanic was not informed about the water marks by the service advisor which was disappointing and probably made the day a complete waste of time. For this visit I was charged half an hour of labour at AU$170. Anyway I have picked the car up and will monitor that left hand tail light area. Hopefully this time they have solved the issue. Having owned 2 previous ML's over 15 years I have never had to clear a sunroof drain and have never had water ingress because of it so.... Will put an update in future to confirm if problem is fixed or not.





The middle cargo rail support is under suspicion...

 

Yep, the bolt that goes into the roof to hold the rails in place is a known leak spot. The only way to really fix is remove the entire interior roof panel to get to the screws so you can take everything out and redo the seal. Crappy sealant causes the issue.

 

I am currently running a thread about the issue with the clogged drain tubes now. I have consulted an attorney and we are trying to determine if there are enough people for a class action. The thread is here: https://mbworld.org/forums/general-m...ain-tubes.html

Good luck on the repair!

 

Fuel system, diesel, fuel system, gasoline

Recall date
2022-12-23

Recall no.
22V955000

Mercedes-Benz USA, LLC. (MBUSA) is recalling certain 2012-2014 ML550, 2012-2015 ML350, AMG ML63, 2015 ML250, ML400, 2016 GLE450, GLE300, 2016-2018 GLE350, GLE550, 2016-2019 GLE400, 2017-2019 AMG GLE43, and 2016-2020 AMG GLE63 vehicles. Water might accumulate in the spare tire wheel well and damage the fuel pump control unit, which could cause an engine stall while driving.
Recall consequence
An engine stall while driving increases the risk of a crash.
Recall action
Dealers will install a water drain plug, inspect for water intrusion, and replace the fuel pump control unit as necessary, free of charge. Owner notification letters are expected to be mailed February 21, 2023. Owners may contact MBUSA customer service at 1-800-367-6372.