OK, what is this px from? two 123s several years apart have the same problem. Pooling water in left back passanger floor. Also a substancial amount of water accumulates in the trunk.

These are a 79 300D and a 83 300TD.

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79 300d
83 300td
75 XJ-6 coupe (JAG)

Leaky window gaskets are notorious on the W123s.

the trunk problem could be the tail lamp housings leaking.. i solved mine with some clear silicone caulk

Thanks, I am sifting thru all possible causes. To date I have given both 300s
a solid soaking. On both the only leak common to both of them is a cascading leak on the passanger side, under the hood at the hood spring mount / battery box location.

This leaking area is a direct source of water going directly from the hood spring mount area to the passanger side front floor and then to the back passanger side floor where it stops and pools.

I will be tearing out the battery and battery box as well as looking for blocked body drains, just as soon as we get a nice enough day here in Seattle.

I feel like a tasmanian demon burrowing after its' prey....

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79 300d
83 300td
75 XJ-6 coupe (JAG)

Hi,

I have the same problem with water pooling in the floorboard of the back passenger area. Was your leaking problem related to the area under the hood or did a rear window seal fix the problem? I'm also West Coast (San Francisco, not as bad as Seattle) and I'm in the heart of the rainy season. It would be great to find this leak.

-Eric

i'm having the same problem. when i go to work it's dark, same when i get home! my house was built in 1926, so my MB won't fit in the garage and i have a three year old i spend time with. good thing i found this problem before i put new carpet in! i need a clear saturday to work on this....i'm tired of this problem being in the back of my head day and night!

I restore Mercedes , and from my own experience water leaks in the front drivers side are almost always behind the brake booster and behind the fuse panel at the fire wall and the way they were engineered sometimes the water rolls down at the cowl and either leakes behind the fire wall insulater or in the hinge area on both sides w116 are very common for rust behind the fuse panel and the brake booster running all the way down to the rockers, I have fixed several by cutting out all the rust and making new panels to put into place, I have also made my on draines to fit into below the hinge area to drain away from the fender area there is aready a drain behind the front fenders, hinden , but I make new drains for the hinge area. Other then that they are all known to leak at the seals on the trunk lid sometimes rust under the trunk gasket that you might not be able to see and the tail lights Pull your tail lights and run a small bead of sealer around the gaskets and put them back in if you try and buy these you can get them but they are expensive. I have done extensive rust repair on all the older mercedes . I have a w116 in my shop now that that has bee soda blasted and striped new rocker panels new fenders and extensive panels replacement for rusted areas,I am a firm beleiver in por15 under the car after being primed with por. it will never rust I have por15 behind fenders , fire wall, inside trunks. I love to work on them, and I do own one totaly restored W116-300-sd 1978 and yes it does run on vegi oil, peanut oil, bio diesel, its paid for and it pays for itself every day cheap and comfortable. I am doing my part for the world and love every minute of it.

I had this problem and it took 2 years to figure it out. I took out the battery tray and the issue was obvious. The hood hinge pocket drain got plugged sending rain water under the battery tray where a hole rusted through the firewall. The water goes under the front carped to the back (downhill design of floorboard). It pools in the back passenger footwell. Fixed with epoxy putty, silicone sealer, and rust inhibiting paint.

1983 300D 203,000+ Original owner - keeping indefinetly