W205 water leak seat rail?

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DocDick

New Member
Joined
Dec 8, 2020
Messages
8
Location
South West
Car
C250
Apologies in advance as I'm not a great technical guy, but I hope someone may be able to help.

I have a 2015 C250 saloon (W205 ?) which has just enjoyed a four week period of rest due to the excitement of a new vehicle. The C250 has been parked outside on our drive facing up a slight incline. I recently noticed a lot of condensation and upon investigation found the inside covered in mould and about three inches of water in the offside rear footwell.

I have cleaned up the mould and nearly completely dried out the car (about 60 hours with a ceramic heater locked in it), during which time I've been trying to work out where the water was coming from. The water was not obviously contaminated (I had to syphon it out) and returned in decreasing amounts over the next few days until I'm now nearly dry.

Checking the carpet by touch, there was no evidence of water in either near-side footwell, nor the driver's footwell. The carpet in the rear NS footwell only felt wet on the flat, where it went up the walls remained dry to the touch, at least. One late night progress check with a torch showed a faint trace of water tracking along the right hand rail of the driver's seat (the left rail of same seat was dry); wiping it dry with some tissue it became faintly wet again after a minute or so (photo to show where I mean, could not adequately show water).

I'm now at the point where the only water detectable is when I compress the carpet around the end of the seat rail, so I'm not sure if I've won the battle yet, but I'll run the heater for another few days.

Does anyone have any idea what the source of the water might be, please? I should also mention that the parking brake warning is showing (and appears to be locked on) which may be relevant, or just a problem due to lack of use.

My thanks in anticipation...this-one2.jpg
 
Has the car ever been damaged? Could be an out of alignment with a door shut rubber...
Its going to hard to find...
I think the dealer can perform an internal smoke type test where a smoke device is set off inside the car...with doors and windows shut and it will escape from the offending area...
Also you could do the reverse by sitting the area with all doors and windows shut...Get someone outside with a decent pressure hose....get them to spray around the door shut and window shut areas...while you are looking / feeling for any ingress....
Also maybe a blocked drain channel somewhere...again the hose test could help locate it....
Good luck with finding and fixing it as...condensation build up inside is a pain in the backside...
 
ioweddie

Thanks for your helpful ideas. I'm originally a biologist, so may be over-simplifying things but, having identified water repeatedly tracking along the seat rail, I wondered if that might ring a bell with someone who knew the anatomy of the car rather better than me. If enough water had got in that way, sufficient to form a 2-3" deep reservoir in the rear O/S footwell, that may well have been the source of the condensation.
 
If you've had 3" of water in the footwell that will be the source of the condensation I would think. Obviously a serious leak ( No chance of a window being left slightly open?) - I would be checking the door and window seals. As Ioweddie says a smoke test will indentify if there is a defect there - you can do this yourself. Another possible source might be the drains to the sunroof if you have one. I'd be tempted to remove the rear seat base and see if there is any evidence of any water tracking from the rear quarters or the boot.
 
If you've had 3" of water in the footwell that will be the source of the condensation I would think. Obviously a serious leak ( No chance of a window being left slightly open?) - I would be checking the door and window seals. As Ioweddie says a smoke test will indentify if there is a defect there - you can do this yourself. Another possible source might be the drains to the sunroof if you have one. I'd be tempted to remove the rear seat base and see if there is any evidence of any water tracking from the rear quarters or the boot.

Hi can you please tell me how to do the diy smoke test

so far my car was leaking from , rear lights, read tailgate seal, rear tailgate handle, bumper vents and filling battery from blocked drain, all common issues im told, I would like to see if I got all the water ingress points


Many Thanks



Tezz
 
Hi can you please tell me how to do the diy smoke test

so far my car was leaking from , rear lights, read tailgate seal, rear tailgate handle, bumper vents and filling battery from blocked drain, all common issues im told, I would like to see if I got all the water ingress points


Many Thanks



Tezz
You can hire a smoke machine (which is best), but the cheapest way is to buy smoke pellets from Screwfix or similar. Cover up carpets upholstery dashboard etc and light a pellet in an empty tin. Obviously close windows doors boot vents etc. Any possible leak source (apart from blocked drains) should be spotted straight away. Won't work in the engine bay for obvious reasons.
 
It could be the vapour barrier behind the door card, front or rear.
The butyl tape gets brittle and allows water to run inside the car.
You can buy the tape cheaply on the internet.
 
Well, Mercedes Assist came out (the parking brake was electronically locked on, maybe due to water ingress) and took away the interior door sill to quite clearly show it was wet in the channel carrying part of the wiring loom. The vehicle has now gone to the local dealership's workshop for investigation/damage assessment.

In conversation, the tech said that if a partial replacement of the loom was necessary due to corrosion, MB have to tailor make that portion of the loom (or, indeed, the whole loom) from scratch, as there is so much variation even within same model range, that it's not an 'off the shelf' option. He spoke of several weeks being possible just for the manufacture. Has anyone else encountered this?
 
Yes wiring looms can be a problem,all the big car makers source their looms from the far east,South Korea is one of the big suppliers,your car being 5 years old will have a type of loom not fitted now,and has been found before on here MB do not fit just one loom and then just use the connections needed for whatever options the buyer has chosen,and so there are lots of different looms,and I suspect that a supplier like South Korea will not give to much impotence to a restocking order of say 30 looms so the delay,just maybe with the damaged loom out they will get a local loom guy to make one but that is a very long shot,years ago looms were bought from the uk,and there was small companies who made special looms but I suspect they are long gone,hope it does not take too long before your car is on the road.
 
Manufacturers are required to be able to 're-manufacture' certain items within a five year period of first release , I have no idea if this includes wiring looms but I would doubt it as they are so varied even in the same model. In this case I would doubt the whole loom would be replaced as already stated.

If this turns out to be a fault rather than a blockage of a drain it would be a pretty poor show for a 5 year old car...any car.
 
With thanks to all of you who have contributed to my understanding of this problem, as well as my appreciation for your support.

I shall provide an update once MB explain the issue to me, just in case it adds to the pool of knowledge on here.

My best wishes to you all for an enjoyable Festive period - it's going to be different, that's for sure, but keep it safe.
 
Water in the footwells could come from front and back of the car. I'm assuming your area of cause has been found, but I thought I'd chuck a few ideas on the thread.

Common causes of boot leaks here:

Door seals often have tiny holes or nicks designed into them and the corresponding seal (if there is one) on the body work. These are intended to allow water to drain round the door and out past the seals. There was known issue in recent years with some of the VAG cars filling up with water due to seals creating a reservoir of water in the door. A technical release was done with replacement door seals, now with holes/nicks in the correct place. The seals had to be fitted very carefully to make sure the intended holes were in the correct place after fitment. Dealers often knew nothing about it so totally fobbed customers off or stated as fact it wasn't the case, or claimed/charged for the new seals whilst simply taking a stanley knife to the existing steal to create a nick as part of the customer experience. You might call if fraud. I couldn't posssibly comment.

As already mentioned, sun roof seals and drain points. The start of the drains can be located with the sunroof open. Carefully pouring water into them and watching it appear successfully under the car is the 'all okay' test if they appear clear from the top.

Under the scuttle panel where the wiper bases are, there is a drain system. If this fills up with crud the rain water drainage is reduced/blocked, and the drain can fill up with water and flow usually into the passenger (left front) footwell from the heater/blower matrix/box, and then flow to wherever within the car.

If the aircon drain blocks, the moisture removed via the aircon system builds up in the system and eventually flows. The aircon system lowest point and drain are usually located in the bottom centre of the dash hidden deep away. Again, usually the front footwells first, could be either side of the tunnel between the driver and passenger footwells. This can usually be inspected from under the car if the tech knows where they are looking for the aircon drain hole from underneath, buried somewhere near/above the transmission. Incidentally and totally separately, if you had a suspected aircon evaporator matrix failed, it would be this drain point you would look for signs of PAG oil or UV dye if the system had UV dye added.
 
Right (still reeling from news from Mercedes!)... They haven't worked out where the leak has come from yet (that test's going to be £350), but there's corrosion to the wiring loom that runs in the channel under the driver's side: new loom and various electronics to be replaced, new carpet etc and labour come to a few pennies short of £8,000. There's also a note that further dismantling to investigate the source of the leak and put it right could add significantly to the total.

The insurers don't want to know ("Yes sir, if you'd driven it into a flood you would have been covered, but not for water damage caused by rain ingress!"). Local Mercedes dealer's initial reaction that they are very unlikely to contribute towards it (the car was bought from them, as was its predecessor about 8-10 years ago, and has full service history from them). Several quotes indicating value of car in repaired and roadworthy condition about £9k.

So, a car just under six years old is likely to be written off as an uneconomic repair. Breakers have offered £3-4k sight unseen.

Disappointed.
 
That's really bad news :( . But at just 5 years old (how many miles ?) unless the car has been poorly repaired after crash damage or you have been really unlucky with drain blockage you should not be experiencing this unless there is a build fault.

How long have you owned this car ?
 
Might be worth paying for an independent inspection. If the cause can be put down to MB failure you might have a case ... 🤷‍♂️ You say MB want you to pay £350 for them to find a fault that might cost them a lot of money to fix. As honest as they may be it is not in their best interests to find a fault with the car that is their fault.
 
The car's 5 years and 9 months old, and we've had it since it was taken off the dealer's demonstrator list around 6 months after it was first registered.
We are the first private owners and it's done around 76k miles. All servicing done by Mercedes dealer from whom we purchased it. Only crash damage is a slight nudge to the rear bumper which remains unrepaired.
Most likely (i.e. hypothesised but not proven) cause of damage is accumulation of leaves in wiper scuttles blocking drainage channels, which then overflowed and entered cabin somehow.

MB damage assessment photos reasonably convincing regarding corrosion on some block connectors, and accounts for one or two electrical issues that manifested themselves at the same time as the flooding of the rear O/S footwell. Car was parked uphill on a 30-ish degree slope, so easy to see why any water ingress collected in rear footwell.
 
That is bad news,I would get a local mobile electrician to sort the loom out and he might well take the seat out so the carpet can be dried out,but I suppose the big question is where is the water coming from,if the door seals are ok I would discount them,and then look at the boot seals make sure the floor of the boot is dry,then turn your attention to the drains on the scuttles my S gets like a paste of dirt and crap which need to be helped on its way,at least you have got pictures of the loom for your money,:rolleyes:
 
I saw someone trace a leak before by taking the carpets out and spreading talc powder about it will leave a trail where the water is getting in, I am sorry to here your story let us know how it pans out with merc, they are taking the piss 8K
 
... I am sorry to here your story let us know how it pans out with merc, they are taking the piss 8K
Thanks for your kindness. True they are not making things easy - am awaiting their valuation for it as a trade-in *IF* all the work is done. Webuyanycar.com offer about £10.5k, although that's for a motor with an several months MoT and in good nick: it's fair to say that ours could reasonably be described as well used, at least in body terms. So, assuming the worst, their valuation is the same cost as putting the car right, scrap value is already established at £3-4k. Therefore, exploring other route of trading in with Mercedes, although it sticks in the craw....

I have quite a strong but sad feeling that the breakers are likely to be the best option, if only as an expression of dissatisfaction with/to Mercedes!
 
Most likely (i.e. hypothesised but not proven) cause of damage is accumulation of leaves in wiper scuttles blocking drainage channels, which then overflowed and entered cabin somehow.

I'm making a leap from the W212 and almost every other personal car I've worked on, and I'm assuming it applies to your w205.

As I said in post #12, if the drain blocks, water can fill and get in though the top of the heater box.

Watch this vid for swapping the battery, but at 2min 11s it shows the likely entry into the cabin. You can see the cabin blower drum clearly visible
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If you remove the scuttle panel, you will be able to get access to the drain channel.
Get one of these pullers to get the wiper arms off as part of the process. Watch a video on youtube to see how to remove the arms. But use the puller, don't just yank the arms off like some idiots show you!

Also watch out for wiper jets/pipework clipped into the underside of the scuttle panel.

This is an easy DIY, and will take easily less than 2 hours from start to finish including a thorough clean.

I used a flexible crevice tool attached to my Titan industrial wet and dry vac; dry first, then bag out and used wet with a hand-held water pressure sprayer and aquarium pipe cleaners.



 

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