I regret to say that the Mercedes mechanics who designed the 123 chasis made some serious mistakes. One of these is the battery location and tray. I mean, if when a battery heats up it dribbles highly corrosive electrolytes everywhere, isn't it counter-intuitive to put it over a critical metal area?

It seems like you could just run a rubber hose off the battery overflow valve down to the bottom of the ground so it drains out there, but I guess that would have been too easy.

Irregardless, it seems that the previous owner of my 83 300cdt (my father, a chronic neglector of cars...he now has a Fixed Or Repaired Daily explorer which has a grinding differential ready to lock up any day) did not think up this innovation either, and so there is a gaping hole in my wheel well and the firewall resembles some kind of pliable clay than it does metal.

I'm not sure if it is too large to use some kind of a rust paint, cover-up solution on it. It's more than a little worrying structurally, since this area would crumple easily in an accident. I've looked up body metal, but I can't seem to find it for these cars. I'm at my wit's end, and I'm sick of there being a hole in my wheel well. I JUST WANT A COMPLETE CAR!! Please someone give me some resource for right metal sheet.

Other than this the rust is not that bad....knock on wood, watch it fall to pieces tomorrow. I have a pic attached if you care to see the horror of my plight, what you are looking at is the bottom of my battery tray (also rusted and bubbly and gross, despite my efforts at rust painting it) THROUGH the hole in my wheel well.

The little red wire is the power cord for my amp going through a hole that was already in the firewall (how convenient, at least something good came of it! ) and the shiny reflective thing in the far left background is some new aluminum I epoxied in today to cover the firewall hole to prevent water leakage and sealed with silicon sealant.

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couple things....id say...

the OEM battery / replacement does have a vent tube...i can post picts of mine if you want to see it, and it vents at the bottom of teh car near teh idler arm...

second - do not use silicon - moisture trap...that will cause more problems...

aluminum and steel are not the same...they will not like living next to each other in a area such as you have and will rott at different rates...

most of the worry of impact is handled by the saftey cage and the frame, the little inner wheel well is not a huge problem, but repairing it should be done non the less...

i had the same problem...i started on the inside, ripped all the carpet out - the tarr / ashphalt / black stuff - under inner coating on the floor is a PITA, then pulled the fender (found more rott) replaced the inner fender to the headlight ares) made patches and new steel for teh firewall (not too hard), inner fender, mig welded it all back togther - and sealed it all with 3M drip check...

its alot of work ( i guess - a wekend worth), and id bet the farm that there is more rott hiding in that car than just under the battery, although that is a bad spot on a W123...

its steel
Jake

Oh where oh where has my wheel well gone, oh where oh were can it be. This dity is to be sung along preferably in harmony when doing the replacement to make the time fly. A nice neat repair may require cutting out replacement metal from a donar car. This project is basically low cost but lots of elbow grease. Many areas on this model can require a simular type of attention.

This is not a total loss. I have seen classic Mustangs with much worse.
Your going to learn about a product called POR15.
They have a web site.

http://www.por15.com/

They have all sorts of products that will correct this flaw.
I would suggest the POR15 epoxy putty and then cover the area with POR15 paint.
Buy their products, all 3 to do the repair. Metal ready, Marine clean and POR15 paint.

It's not cheap but it works very well.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Any battery that is oozing acid is being severely overcharged. At most, they might gas off a bit. You might want to check your voltage.

__________________
1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer

I was told that this fender rust was a result of a leaking battery. It is from a TD.

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__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

I think all the lead acid batteries burp a little from time to time, yes it was a poor design. With my current setup I have a acid mat under the battery (from PP) and a hose from the Duralast battery (that won't last) most of the way to the ground. Soon I plan on replacing this with an Optima 34R so no more worries about leaks or failing batteries.

If it feels mushy that means there is no good metal left, it is the undercoating holding that whole area together. Probably your best alternative would be to get that metal out of there and use a panel adhesive to "glue" in some new 20 or 22ga sheet metal. Many vehicles now days use panel adhesive to hold things together so it is strong stuff.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

I still wouldn't use panel adhesive in the capsule around the passengers, meaning the firewall, floors or roof, etc. It is easier for me to say this 'cause I have a welder.

glue works, and its very oem on cars and planes....but


WELDERS RULE!
jake