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A few days ago, after owning this car for a few years, I noticed that the front left head lamp had some heavy moisture behind the lens. After searching this forum I found it seemed to be a common issue and that MB considered it "normal", but the odd thing is that the right light showed absolutely no signs of moisture.
After some investigation under the hood, I couldn't find any obvious signs of liquid ingress.
Looking from the bottom by the wheel arch I realized there was a panel missing right being the headlamp, which meant that any water or debris from the road was being flung by the wheel during rotation right into the back of the headlamp assembly, with the wiring harness being the closest to the wheel. Which is obviously a bad thing to be happening as these head lamps are costly to replace.
I found the source of the liquid ingress. On the back of the headlamp assembly there is a round dustcap that has a small rectangular membrane (that allows air pressure in and out while keeping water and vapour out) that had been damaged by the debris from the wheels.
It has been raining daily, so while I have been driving the wheel has been propelling water directly into the hole and that is why the headlamp was filling up with so much water.
I have since done a quick fix on the hole as a temporary solution, and also ordered a new dust cap with membrane to replace it.
I now need to replace the part missing from the wheel arch to prevent any further damage to the headlamp.
I have no idea if it was already missing when I bought the vehicle or if it fell off while driving.
My question is: does anyone know what the part number is for that small rectangular panel that forms part of the wheel arch? Or where I can buy one?
I can't find it online, only the entire wheel arch assembly.
Or if someone with an X166 could check the part for its number so that I can hopefully source one online. Front left wheel arch, just behind the headlight assembly
It’s an access panel. If you didn’t find it online at mbparts.mbusa.com or similar it isn’t available separately.
Options would be buy a complete new wheel arch liner, or see if a salvage yard will sell you just the access panel. Or stop by a couple of dealers with the puppy dog look and ask if they have any hanging around that fell off or were found from other vehicles.
Aside from missing the fender liner cover, looks like you're missing the cap to close off the headlamp which is why all that water getting kicked up into the fender is getting into the headlamp.
Aside from missing the fender liner cover, looks like you're missing the cap to close off the headlamp which is why all that water getting kicked up into the fender is getting into the headlamp.
Yes, that is the dust carp that I was referring to, it is removed in the images as i had taken it off to repair the hole that some debris had caused the water ingress was due to that hole
Thank you. I think I managed to find the part itself under the part number A1668841000, but it is listed as a part for the W166 (ML) on the MB website. so it arrives tomorrow and I will see if it fits.
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