Fixing Battery Tray Rust Holes...advice needed - PeachParts Mercedes-Benz Forum

dieseldan44 · #1 05-07-2007, 01:15 PM

Gents,

Took this saturday to focus on the only rust on my TX car - neglected battery tray. As I tore into it and removed some of the crumbly stuff low and behold there is also a big hole in the firewall near the passenger footwell. Doh. (see pics) Thanks PO!

No sense crying over spilt milk, time to fix it. Whats the best course of action? Here's my plan Ive gleaned from archives:

1.) Already wire brushed, cleaned with POR-15 marine clean, applied their pre-primer 'metal ready' to it.
2.) Will POR-15 the heck out of the area.
3.) Fashion sheet metal plates to fit well over the two major holes. Screw in.
4.) Bondo over the affected areas, hit with some primer and undercoat.

Does this sound about right? Need advice...don't want to regret how I did this later on. I'd like to take the time and do it right. Doesn't have to be pretty...just solid.

Thanks in advance,
dd

F18 · #2 05-07-2007, 03:15 PM

You need to remove more than just the crumbly stuff. Use a cutting wheel or even a Dremel Drill with the mini cutting disc and remove all of the rusted thin metal. What you want left is the normal gauge metal may be with a little surface rust. Fashion your sheet metal plates of similar gauge steel to fit the contours. Old appliances are a great source of sheet metal ie. refrigerators, microwaves est.....and the quality of the steel is sometimes better than the steel used to make the cars.

Idealy you want to weld the patches/plates in place with a mig welder. If you don't have access to a welding unit and the area is not structural then rivet or screw it in place. Clean/grind/sand the area again after patch is in place to remove surface rust then prime with High Zinc Primer (the higher the zinc content the better to deter new rust!).
POR-15 does not repair anything! All it does is seal existing rust and mask the rust damage already done so you can paint over it. The same for Bondo and glaze....its a blemish remover!

To seal the seams after everything is secured , clean and primed use a caulking tube of Automotive Seam Sealer (3M makes some in gray) You can prime and paint over it when cured.

Everytime I tackle a new classic car body project I go to the library and take out a book on autobody work to give myself a refresher. You always come a cross a new trick you did'nt know about.......

Good Luck

pj67coll · #3 05-07-2007, 03:19 PM

Surely welding is better than riviting? If you cant what about using JBWeld as the glue? My car has the exact same hole which a PO had patched with fiberglass. Dont think that's really an ideal fix though. I'd prefer to use steel.

- Peter.

bgkast · #4 05-07-2007, 03:22 PM

My car has been fiber-glassed in that area. Not the way I would have done it, but it seems to have worked fine.

From best to worst repair you could:

cut the whole back to good metal, make a patch panel the exact size of the hole and butt weld it in then paint.

cut the whole back to good metal, make a patch panel larger than the size of the hole, weld it in then paint.

cut the whole back to good metal, rustproof, make a patch panel larger than the size of the hole, rivet/screw/ glue it in then paint.

cut the whole back to good metal, rustproof, and fiberglass.

I have had good luck using the patch panel/glue method for fixing a hole in the trunk corner. As long as it is not a structural issue this is the method I prefer (other than the butt weld option which is a big pain) because it allows you to fully rustproof the area before the patch goes it. If you were to weld, screw or rivet the patch in there is going to likely be some unprotected metal in the repair when you are done. I use an automotive quality adhesive/sealant for the glue. Many new cars are held together with the stuff.

F18 · #5 05-07-2007, 03:26 PM

Peter......If it were my car I would only weld! No JB Weld...No Bondo....No Fiberglass (unless it was a glass body). Welding is the only perminent solution to metal repair.
Cheers

junqueyardjim · #6 05-07-2007, 06:21 PM

If you are, it could be welded. However, for that same rust hole on mine, and because the patch went up one wall and also had to fill the damage on the flat part, I cleaned it well and painted it with POR. Then I took a properly sized piece of plastic including the curve in the side of plastic Vegetable oil cube. I ran that piece of plastic through the dishwasher at least twice, then broke the glaze on it with sandpaper. I then glued it down with JB Weld. That was two years ago and I looked at the repair recently, no further rust, the patch is holding perfectly and I think for being under the battery tray, it is a perfect fix. I believe that ultimately the car will go to the crusher, with that patch area looking very good.

Eric Eliel · #7 05-07-2007, 07:03 PM

That is a replacement part and might be available aftermarket. Its cheap stamped steel. Too much work to repair. Call Phil.

JimmyL · #8 05-07-2007, 07:26 PM

Quote:

Originally Posted by bgkast

I have had good luck using the patch panel/glue method for fixing a hole in the trunk corner.

I would love to see a pic of that repair if you have it. Basically, the whole drivers side trunk well is gone on the Squash! I have to be careful what I carry in the trunk as it is big enough for a football to fall out of!

Quote:

Originally Posted by Eric Eliel

That is a replacement part and might be available aftermarket. Its cheap stamped steel. Too much work to repair. Call Phil.

The above discussion is about the firewall, not the battery tray...

300SD81 · #9 05-07-2007, 07:33 PM

I'd like to see a plastic replacement battery tray.. I normally prefer metal over plastic, but this is an exception... The acidic environment just promotes rust...

Rashakor · #10 05-07-2007, 07:34 PM

I would not go with the fiberglass/polyproprilene option...
But I would not go either with the welding option either.

I have seen Urethane based repairs (POR15 is a moisture-cured urethane) outlast the car on which they were put on. On that particular spot, under the battery, I actually thing it is not only the best option... it is the only viable one!!!. A weld will actually rust much faster unless you urethane coat it. Might as well just use glass fiber cloth and the urethane in the first place. In case you don know, that spot has actually from factory a translucent glass panel... there was not much metal there to start with.

bgkast · #11 05-07-2007, 08:04 PM

Quote:

Originally Posted by JimmyL

I would love to see a pic of that repair if you have it. Basically, the whole drivers side trunk well is gone on the Squash! I have to be careful what I carry in the trunk as it is big enough for a football to fall out of!

Mine was not quite that big. See post 8: http://schumanautomotive.com/forums/showthread.php?t=3070&highlight=rust

The same technique could p be used on a larger hole as long as it is not a structural area and there is solid metal to bond to.

This repair was done on the 240D I sold this year and I forgot to take after pictures. Unfortunately the new '85 has the same problem so I will try to do a better job of documenting the repair this time.

dieseldan44 · #12 05-07-2007, 10:43 PM

Thanks for all of the replies, there are certainly a lot of varying opinions on the subject.

I do have access to a welder but the area I would need to do the welding is pretty tight,and wouldn't I have to do a lot of surface prep in the vicinity, de-undercoating etc.?

Even if I welded the area, wouldnt a topcoat of POR15 be a good idea?

Dewhite2485 · #13 05-07-2007, 11:44 PM

Im in the process of rust repair also, I have the same hole as your all talking about and havent decided what Im going to do to fix it yet. Welding I would think would be out of the picture unless you pull the dash, the AC box and the insulation off the fire wall otherwise you will have a nice fire, one thing I havent seen anyone talk about is panel glue allot of new cars have glued together parts coat it good with rust inhibitor and glue on a patch should be good as new and sealed up. My big problem was the thing leaked for so long that it rusted out the passengers floor pan a bit so I have to fix all that too but o well its a 20 some year old car its bound to happen

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