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1979 450SL UK spec
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Discussion Starter · #1 ·
My front right side floor panel looks like this. So I'm trying to decide whether to weld in a patch or fit a new floor pan.

Does anyone have experience of cutting out the old pan and fitting a new one, was it straightforward or tricky?

 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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14,174 Posts
Does your MOT have anything to say about how sheetmetal repairs are done? Here in Ontario, Canada, we have new regulations that specify how patches should be made in order to pass inspection.
 

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1979 450SL UK spec
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2,917 Posts
Discussion Starter · #6 ·
Does your MOT have anything to say about how sheetmetal repairs are done? Here in Ontario, Canada, we have new regulations that specify how patches should be made in order to pass inspection.
I think they say that they must be seam welded along the full length of the new patch, my goal will be to make it look like there was no repair in the first place.
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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14,174 Posts
This is what our regulations say. I had floorpans on my 300D welded before these regulations came out. All covered by sound insulation on inside and undercoating on outside. Not sure how they would check it.
 

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1976 450SL
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657 Posts
My front right side floor panel looks like this. So I'm trying to decide whether to weld in a patch or fit a new floor pan.

Does anyone have experience of cutting out the old pan and fitting a new one, was it straightforward or tricky?
I've done both. On the LHS (Drivers) the floor plan was rusted pretty much front to back, so I replaced the entire thing with Mercedes parts. On the RHS the damage was much more localized - it looked similar to yours.

I'd say that if the rust gets close to either the cross member, or the short 'beam' that runs back from the firewall, you should replace the entire panel - especially if the area behind or under the cross member is affected If it's anything less than that I think a patch is ok (that's the criteria I used).

If you do decide to do the complete panel, you defintely need to remove the cross-member (even if it isn't rusted out). Also, you need to make sure you have a good tool for cutting out spot welds - seemed like there were a thousand of them. The only area that was a real pain was where the panel attaches to the rear crossmember (at the end of the rocker). You need to remove the subframe mount.

Though it looks like a patch is the easiest approach for you, I thought I'd post a few photos of each side of mine, so you can compare the work involved...

-Steve

PS Nice post of the MOT guide - even though I live in a US state that has almost not inspection, I still use my UK MOT experience as a guide when repairing/maintaining my vehicles. I always thought it was pretty fair, and kept things safe without being unreasonable.
 

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1973 450SL, 1999 c230
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I have welded floor pans in a similar condition and passed the UK MOT. By cutting out and replacing the metal the repair will be more than adequate for the MOT. My guess is that you will be making an invisible repair with the correct type of beading... Thats more than enough. I have seen lots of examples of metal welded over holes and significant corrosion without even cutting back the corrosion. The purpose there has been to connect good metal... and pass the test. Your proposed repair will be very strong.
 

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1979 450SL UK spec
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2,917 Posts
Discussion Starter · #15 ·
Yes, its the same car, I think I will spend about 1000 hours on this restoration and when I'm finished it will look exactly the same as when I started.

Here are the "before" pictures, once finished I will post the "after" ones, no one will see any difference except for my MOT tester.

However the car should last another 40 years.











 

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1976 450SL
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657 Posts
Yes, its the same car, I think I will spend about 1000 hours on this restoration and when I'm finished it will look exactly the same as when I started.

Here are the "before" pictures, once finished I will post the "after" ones, no one will see any difference except for my MOT tester.

However the car should last another 40 years...
Wow...amazing how good that looked. I love the blue - that's the color I would have chosen for ours, but as it's going to my wife's car, she got to choose, so has gone for a more subtle shade (Subaru Atlantic Blue Pearl), which I still think will look good with the chrome. I have to ask - was the red interior original with the blue exterior?

-Steve
 

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1979 450SL UK spec
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2,917 Posts
Discussion Starter · #19 ·
I've been distracted from the floor by this other quality repair done by a PO.



I started cutting, bending, hammering, fettling and welding .....









The final result is not as neat as I would like but is as good as I can do, will look find with new under seal and paint on top.

 

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1983 380SL (us), Former owner: 1965 190Dc
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1,457 Posts
This is what our regulations say. I had floorpans on my 300D welded before these regulations came out. All covered by sound insulation on inside and undercoating on outside. Not sure how they would check it.
Would this Reg. include older vehicles with a separate frame?

Utah is actually terminating their vehicle inspection at the end of the year. Not that they checked vehicles for structural integrity in the first place.
 
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