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Fixing rust under battery, need opinions!!


utvolman99

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Okay, I now have a gaping hole where my battery tray used to be. This weekend I am planning on patching the hole and need some advice. I will be moving the battery to the hatch area so I dont have to worry about that.

I am very new to welding (read first time). I have a small mig welder and would like to keep this as simple as possible. I was planning on...

 

1. Cutting and bending a patch that will roughly fit the hole

 

2. using sheet metal screws to hold the patch in place

 

3. welding the overlapping seams on the top and the bottom

 

Is it okay to do a lap weld?

 

would a butt weld be easier?

 

could I solid weld the top seam, spot weld the bottom them follow with seam sealer?

 

Sorry for all the questions any help would be great!

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Well, im in the same position you are. Big hole under the battery, never welded before. But from what the professional welders tell me butt welds are better to lessen the chance of moisture seeking little crevices. Make a patch panel then tack it to see if it fits correctly, then weld a small section here, then on the other side, then the other to prevent warpage. Then after all the welds are met and finish put a seam sealer if applicable. They all tell me that you just dont want water to have a place to sit down because it'll rust out again. cheers.gif

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Guest Zachb55

I had a good bit of rusting going on in that area too, well actually most of mine was in that crevice between that area and the firewall which had been previously "treated" with a ton of OSPHO then covered with sealant, when i took the sealant off i found about an inch deep seam full of white powder (dry OSPHO) and lots of rust, which was no longer growing luckily... what i did was just welded up any holes in the firewall and put lots of weld in the crevice to strengthen all of that, hopefully it will be helpful. oh yeah, i had to grind out my battery tray to get down to that stuff cause i could see some rust growing down there and im moving my battery to the back anyways so i thought "hey less weight for the front" and proceeded with grindage... good luck on whatever you do, i know from my little experience that forming a patch out of 18 or 16 gauge steel isnt much fun.

 

-Zach

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I'm no engineer but it seems to me that that is potentially a high stress area of the unibody. The front frame rails, firewall, front suspension tower all adding to stress in that area. I would think that a properly welded patch would be the best solution. Also, you should check the firewall and frame for rust damage.

 

Scott

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Now that you mention it that is a good point. I really dont know how much stress is on that area (and I am an engineer confused2.gif ) but I dont think its worth risking more work down the line. So welding it is.

 

By the way there is only light surface rust on the firewall and frame rails so I should be okay there...

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... you might think about making a template of the area - perhaps even a wooden buck - so that you can properly shape the patch and get a nice tight fit that will butt weld nicely.

Also, you should notice that the original innerfender has a flange at the interface of the firewall that you might want to replicate in the new panel. There is also a crease in the original near the frame rail that gives better acess to the grommet for the wire harness that passes through there.

While you're at it, make several copies and sell them as replacement panels! ...no one else does, and it's one of the most common rust areas in a Z.

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UTvolman99,

 

I feel your pain, I am fixing the same problem as well. Just a bit of advise. I had surface rust on my firewall and framerails as well, it did not look nearly as bad as the battery box rust. Fortunately, I had my entire car sand blasted from that I found out that the surface rust was worse than the hole in the fender. As a result I am now replacing the firewall and frame rail. Make sure you strip the paint on both sides and fix the problem now before it goes any farther.

 

Good luck.

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Guest Anonymous

My 2 cents (from a no talent mechanic) Try welding half inch tubing as a frame, then use sheet metal or fiberglass sheet to form the pan. Tubes are strong, and FRP doesnt rust.

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