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A while back I found my 350 leaked inside no matter what the PO had paid mechanics to fix.   A day outside in steady rain would cause all foot wells to be flooded.  By accident I came across the source and to date, have had no further leaks since I fixed it.  I've been self mandated with maniacal determination  to tell you all that if all else fails, check this vulnerable spot for leaks.

So, without anyone else confirming my find since then, I've taken it upon myself to dig into this latest wrecking 280se I've had for a week.

Firstly, I acknowledge that there are few causes for water ingress, but it's my belief, this area is overlooked.

This yellow 280se received about an inch of steady rain prior to me picking it up, has been ungaraged for at least the last two years, has a newer aftermarket windshield seal which seems to be in really good condition with a flawless windshield.  It also has wet carpets.

All pics are clickable for a larger size -

The problem area is on the LHS within the fresh air intake trough, whereby debris and rain cause rust in a lap joint which will spread throughout the trough.  The lap joint is below where the screwdriver sits and is a nightmare to repair.


Access without angle grinder is by removing the chrome intake.  This one had original retaining clips.  They're probably impossible to remove without breaking.  It's a wrecking car so I didn't mess about.  Remove the wipers first with grommets, two nuts and washers, then remove said clips.  Slide a plastic ruler between where the windhield seal rests on the chrome grill.  It may have sealant binding to it.  Lift the grill up and towards the front then lift out screen.


I was amazed at the amount of crud in the trough which I believe hasn't been accessed since the car left Germany many years ago.  But check out the other seals and holes that are attached to the trough.
My 350 had a seal around the wiper mechanism.  This one didn't seem to.  Heater hoses were crunchy and bulging and the grommets around the copper pipe entering the cabin were lifting and cracking.  The wiper motor wires' grommet was gaping open.  All probable sources for cabin leaks.



The trough looks higher on the RHS. The drain hole clear and no sign of rust.  The LHS is deeper and was covered with dirt/sand but the drain hole clear.  I removed the heater hose and that plastic angled shape drain.  The second photo shows the baffle and lip that would stop water from following fresh air into the cabin.  The air goes though that dark space above.


I grabbed a hand brush and with water, gave the LHS trough a scrub.  A lot of dirt.  I ran a small stream of water to try and let the gunk flow towards the drain hole. 

Need I say more.  A fair bit of rust and a decent hole and an obvious leak.

Not sure if the trough for a RHD and LHD vehicle are the same.  With RHD vehicles like this one, water and dirt will settle in this corner.  Particularly as RHD cars spend more time leaning to the left due to camber in the roads whilst driving and whilst parked on the street.






Here's my previous fix for the 350
http://forum.w116.org/interiors-and-exteriors/leaking-cabin-found-the-problem-finally/0/

This is GOLD Oscar, pure gold. The footwell on the back of the white SEL, behind the driver is suffering the same problem. It's the same symptoms!

This is what I'd do -
Before you go popping the rivets off the chrome intake grill, give it a test first by removing your front left foot mat.  Park your car on a slight slope so the right side is higher than the left.  Remove the two rubber drain attachments in the engine bay and plug the drains with rags or whatever you can think of.  Pour about 2-3 litres into the area and see if any water makes its way inside.  Just have to be careful you don't put too much water in otherwise the overflow will go over that baffle I spoke of above and water will come in regardless.   Not only that, but it would be better to test and isolate the trough in that corner first rather than have it leak through one of the grommets previously mentioned.

Also, be patient.  This hole I found was visible only after brushing and probably opened it up a bit too.  But the water made its way regardless.  The 350's leak was slow and no hole was visible, just a sus gap in the lap join.

Here's one of the rubber drain attachments attached and detached.

Do you have any idea if its on the back parcel shelf?

its mainly around the speaker,

regards

NSTG