Join Date: Jul 2015
Vehicle: 2001 SLK320
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I had to clear these on both my cars when I bought them. accumulation of dust becomes mud and blocks them.
Easiest way I found was to remove the boot side interior trim. See Pelican Parts for a start.
Then you can reach the tube ends. The good thing about having these trims out is you can do a good inspection of the rear end for rust, damage and to be sure all the other drains in the lower corners are clear. Inspect for fluid leaks, water leaks and also lubricate the bootlid front locks. Clean out any dust and leaves.
I had tried blowing air and sliding a narrow tube down the drain tubes and flushing, blowing, jiggling, but to no effect.
The tube on my '98 was almost too short and crimped somewhat where it turns a tight corner to go through the side panel. On my '01 car the tube was maybe 15mm longer and a better fit but still had blocked.
I suspect some little spiders like these areas and some cobwebs and dust become the start of a blockage.
So it's worth checking these drains from time to time and flushing them. Also, I never park under trees, as the leaves and seeds
will find their way into the tube.
There is a thread somewhere about putting flywire from screen doors over the inlet grills. I tried this but it is fiddly and hard to make it look neat and harder to see the spiders webs afterwards.