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2005 E320 CDI *black on black with nearly every option*
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949 Posts
Discussion Starter #1
First off, this should be a sticky since it effects a large majority of W164's, and owners typically don't find out about it until AFTER the water has already done thousands in damage.

As many of you know, the W164 ML's suffer from water intrusion problems around the rear tail lights. They also will leak around the tailgate lift arm boot when that eventually develops stress cracks and rips. In the path of both of these water leaks, are thousands of dollars of electrical components that WILL fail when soaked in water. the rear SAM, tailgate lift module, rear fuse box, and the hydraulic pump for the rear tailgate will all get soaked if water is able to enter. $450+ for the SAM, 250+ for the tailgate control module, 650+ for the hydraulic pump, not including any labor.

The solution for this is to get a new upper boot for the tailgate lift arm, and to replace both rear tail light seals, which were installed incorrectly from the factory.

Of the 3 ML's I've worked on over the last year, every single one of them has had water leaking over the rear SAM.
This is an urgent problem, and i highly suggest everyone check their own vehicles to make sure this isn't happening on theirs.
also check your tailgate lift arm BOLTS, since those are known to shear off and is also quite a common problem.
 

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2007 E320 Bluetec, 2008 320ML CDI
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2,430 Posts
Interesting that you warn about the lift arm bolts.
I too had one shear, but the bolt did not fall out.
I found it loose while wiping the car down after a wash.
Fun and games to remove the part in the threads.
It looked to me to be galvanic action, aluminum bolt into steel threads.
I was able to swap the broken one for its partner from the other hinge.
Be mindful that the tailgate is mighty heavy. Would have been useful to have another set of hands rather than working alone.

I used anti seize when I put things back together.


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2005 E320 CDI *black on black with nearly every option*
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949 Posts
Discussion Starter #5
tailgate bolts are definitely not aluminum, They're most likely 8.8 steel. i think whatever coating they put on the bolts for corrosion resistance causes them to back out slightly, and then sheer off from back and forth strain.
 

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2007 E320 Bluetec, 2008 320ML CDI
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2,430 Posts
I recall that the bolt looked like it was aluminum, and there was what appeared to me to be corrosion similar to AL on Steel. The remnants in the threads were challenging to drill. I figured T6.
I’ll bow to your experience on these things.



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2005 E320 CDI *black on black with nearly every option*
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949 Posts
Discussion Starter #7
The bolts would be super easy to drill and be super light weight if they were aluminum.
The engineers also would never use aluminum in a high stress area like that. Haha

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