W164 Water Leak Rear Seal

[E55BOF]

Good evening all.

I have a water leak into the RH rear void below the rear SAM. (Haven't checked the LH void, but I will). My first thought was the rear light cluster, but that would presumably run down the bodywork below the cluster. That may be happening as well, of course, but...

My leak after the recent very heavy rain is dripping down clear of the fuse block on to the deflector plate above the SAM, so it must be free-falling vertically, not running down the inside of the bodywork . It must therefore be either the (fixed) rear side window, or the tailgate seal. (Incidentally, I'd swear the SAM is brand new, or nearly; it certainly hasn't been in there since 2007. It may be the rear light cluster seal has already been replaced).

I found this thread: ML W164 Leak from Tailgate | Bodywork

Lightbulb moment (I hope...)!. Fitting the rear view camera recently, I pulled the seal off to run the wiring across above the roof liner to get access, so it has been disturbed. There were traces of a yellowish-white sealant in places, whether from original assembly or not I do not know. Do I go for silicone sealant all round the seal (fill the groove up and refit the seal - very messy, difficult to get an even bead, and how much do I use?), or surgical tubing? I like the latter idea, but I've no idea what size and wall thickness to use, though there's plenty in many different sizes on eBay. Anybody know?

Thinks: I could perhaps use plumber's putty rather than a silicone sealant? I've no idea. No, tubing would be better.

The OP was on here last year, but has only five posts, so I cannot PM him to ask. Can the mods permit me to send him/her a message?

 

[E55BOF]

At the end of the day it was just the usual taillight cluster seal; the water was dripping from the lip of the bodywork cutaway on to the deflector plate, not running down on the inside. Silicon sealant around where the seal meets the metal , and the groove the cluster edge makes in that seal for good measure, seems to have done the trick. I've put a small towel in there, with a sheet of Kimwipe on top to provide a witness mark if it is still leaking, and will take a look after every rainy day for a while just to be sure, though.

 

[E55BOF]

Rained overnight; still leaking a bit; new gasket ordered from MB Newcastle.

I'll try one of the cheap 'n cheerful Chinese ones for the LH side, but that's less crucial; no SAM there.

 

[E55BOF]

New gasket fitted; still leaking. If it's parked facing up a slight slope, it doesn't leak, so the water is plainly running down the top surface of the cluster to reach the foam seal. I wonder whether this:

WATER LEAK Window Windscreen Leak Water Sealer Sealant Thin Liquid Seek Seal | eBay

Fast Acting Water Leak Sealer. IT IS NOT A THICK SEALER. SEEK 'N' SEAL is avery thin silicone waterproof liquid. Silicone Liquid SEEK 'N' SEAL. It is liquid rubberised silicone. Apply with the long nozzle behind rubber seals.

www.ebay.co.uk

might be the answer? Park the car facing down the slope, squirt the sealant in liberally along the top of the cluster where the water must run, fingers crossed and hope... Easier than taking the cluster out yet again and running silicone sealant all the way round all the edges of the foam seal where it meets body work, at least.

 

[Jobsworth]

Are you sure it’s not the side window? They have a white plastic locating peg that used to let water in back in the day

 

[E55BOF]

The load area windows are fixed, and I've seen a little water dripping off the metalwork of the bulb carrier, so I don't think it's the window.

 

[Jobsworth]

Yes, the bonded ones still can leak. When they are being assembled there is a small white peg used to set the position of the glass for the bonding then to set. They used to leak at the peg and it would drip from the end of it where it protudes into the void.

 

[Jobsworth]

Quick and dirty google for a picture. Peg is bottom left. You’ll need imagination to get the orientation of the window

 

[E55BOF]

No imagination needed; that's a left side window, and it's obvious how it fits. Unless it's a right side window, in which case I'll eat my own underwear...

Nothing dripping from anywhere but the rear cluster, I'm afraid.

 

[Jobsworth]

No imagination needed; that's a left side window, and it's obvious how it fits. Unless it's a right side window, in which case I'll eat my own underwear...

Nothing dripping from anywhere but the rear cluster, I'm afraid.

It’s right side

 

[Jobsworth]

MERCEDES-BENZ M W164 Rear Side Body Window 1646701011 | eBay

Model:M (W164). Right Side - Driver side in the UK or Passenger side in the EU. If parts fits only RHD or LHD cars, this information is stated in item title. Warranty covers only item price paid and for the item, labour excluded.

www.ebay.co.uk

 

[E55BOF]

Gotcha...

(No imagination needed; the car's right outside. If it wasn't, imagination would definitely have been needed).

 

[E55BOF]

Thinking about it, it occurs to me that it's perfectly possible that the plastic plug might be leaking as well as the foam seal/light cluster joint. If it is, how does one get at it to seal it? I can't even feel it, let alone see it, in the void above the light cluster. Does all the trim have to come out to get at it?