Yeah so you mean it would be easier to replace the whole thing even though there would be more actual welding? I am also worried that patching it would increase the risk of the rust coming back at the welds or on the bits I didn't do but I guess that's to do with prep.
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BrokenBiker
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Hard to see from the pic but the inner and outer sills will meet at the bottom at the flanged faces and are usually spot welded, so plugs will be fine for repair work, but I'd say you are going to have more than just an outer sill to do, and the only real way of knowing what's in there and how it goes together it to carefully remove the outer sill, leaving enough meat for finishing cuts to match the repair panel...then offer the new panel up and see where everything meets and how it all lines up.
Not a job for the faint of heart, keep the door closed for the duration of the sill being off to retain rigidity and keep everything lined up.
I stopped faffing about with cutting and patching a while ago, if I'm to do a silly repair, I'm doing the whole sill unless the rare occasion pops up that it is only a small hole to cover
BrokenBiker
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The rust returning is largely down to how well you prevent the rust from returning...you need to cut all rust out, then weld new metal to good metal...after that it's down to how you paint it with decent primers, decent paint etc...but the issue I always see is that even if you cut the rot out, the sill is basically a hollow tube, so the rust will still in there at some point...hence why I prefer to just replace the panel as one, plus you get a really good look at what's under that sill...more often than not, there's rust you couldnt see before. Plus you can coat the inside of the sill panel with weld through primer to give it a fighting chance
As for the more welding aspect, it's not as much as you'd think...you will need to fully weld along the top and edges, but at the bottom where the flanged meet you can drill the new panel and plug weld along the flange to the inner sill...
Yes this is what I thought. There is an inner and outer sill that meet together but there's this other bit of metal in there as well that's what confused me.
The red bit is the inner sill and the blue bit the outer sill. There's this metal in the middle that has big holes in it (the green bit) that has rusted away and doesn't appear attached.
The flange of the red part of the inner sill is very rusty at the back and flexible and crunchy.
The red bit is the inner sill and the blue bit the outer sill. There's this metal in the middle that has big holes in it (the green bit) that has rusted away and doesn't appear attached.
The flange of the red part of the inner sill is very rusty at the back and flexible and crunchy.
I take it this is because it's not worth the extra effort and doesn't do a proper job in the end?
Thanks for replying and your advice. It is very much appreciated.
Misterg
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The green bit should almost certainly extend down and be sandwiched between inner and outer sills. (I don't know your car specifically, but that would be a very common construction - including the (intentional) holes, and the way they rust to nothing at the bottom!)
To sort out what you've described, I think you would need to: remove the outer sill completely; cut away the rusted parts of the membrane panel / middle sill panel; cut away and repair the rotten parts of the inner sill; repair the middle sill and join it to the (now solid) inner sill; rust proof everything then fit a new outer sill.
(I think it would be very sensible to brace the door opening if going this far.)
(Not a professional, just a backyard bodger.)
Thanks
This might be too advanced for me. I don't know how to brace the door or have anything that would do that. Do you think I'll get away with not having to brace things if its just the very end of the inner sill? I wonder if I could just grind away the rust and weld some metal on top of the inner sill.
Misterg
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To do it properly, the middle / membrane panel needs to be repaired. To do that, the outer needs to come off. But if you just want to try and get it through the next MOT...
BrokenBiker
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Bracing doors is easy...I always suggest keeping the doors closed if only doing the outer sill, but if messing with the inner as well you want to make sure the shell isn't going to move at all, so get some box section and basically just weld it where the door should be...you can also use other things if you don't like the idea of welding, I made a prop years ago by welding big M30 nuts to 2 bits of tube, thread them both onto a long bit of threaded rod and now you have an adjustable prop. Some plastic caps to protect the paint and job done although personally I'd weld it.
The doors being closed is good, but cutting the inner sill takes a lot of the rigidity from the shell and the doors may not be enough to hold everything straight after that.
Realistically though, this is the point where it really becomes time to wonder if it's worth it...by the time you have braces the doors, potentially removed seats and carpet (because of the fire risk from welding the inner sill) removed the outer sill and any other internal members, cut and repaired the inner, replaced any metal you removed and then fitted, fettled and welded the outer sill on...you are still only half way through because now you need to prep, fill, sand prime and paint it all, including the sections inside the doors that you welded the braces to
I've doing partial inner & outer sills & jacking points on my Renault Master Campervan recently (not quite finished yet). I'm no welder/fabricator, but needs must...
Visible rust is like icebergs - what you see is only 10% of it.
I ended up cutting out way more than I hoped to (even though I knew it'd go that way).
I chose to not cut away the whole of the replacement outer sill panel area I bought, as it included the upper sill part that runs under the cabin door to the seam the door rubber seats on. I felt I'd keep more rigidity (& the seam & top part of the sill was sound) by cutting lower & butt-welding.
Similarly with the repair panel length.... I cut out the obviously rusted area, and then kept extending till I got to more solid material (I suspect it will go somewhere else at some point, but I'm also going to spray Bilt Hamber Dynax S50 anti-corrosion wax into the sills to try to at least slow the rot!).
My inner sills behind the front wheels (as well as the jacking boxes inboard of those) had rusted as well - I ended up making new inner sill pieces from pieces of 1.2mm Zintec sheet metal & welding those in first, then with that as the centre datum, adding the new outer sill section outside, & the new jacking points on the inside.
It's a bit daunting, but once you get going & actually start, you're committed
.
Visible rust is like icebergs - what you see is only 10% of it.
I ended up cutting out way more than I hoped to (even though I knew it'd go that way).
I chose to not cut away the whole of the replacement outer sill panel area I bought, as it included the upper sill part that runs under the cabin door to the seam the door rubber seats on. I felt I'd keep more rigidity (& the seam & top part of the sill was sound) by cutting lower & butt-welding.
Similarly with the repair panel length.... I cut out the obviously rusted area, and then kept extending till I got to more solid material (I suspect it will go somewhere else at some point, but I'm also going to spray Bilt Hamber Dynax S50 anti-corrosion wax into the sills to try to at least slow the rot!).
My inner sills behind the front wheels (as well as the jacking boxes inboard of those) had rusted as well - I ended up making new inner sill pieces from pieces of 1.2mm Zintec sheet metal & welding those in first, then with that as the centre datum, adding the new outer sill section outside, & the new jacking points on the inside.
It's a bit daunting, but once you get going & actually start, you're committed
.Hmmmmm.
Well it's not the whole inner sill. It's just a 10-20cm bit at the back of the sill at the bottom flange which doesn't go under the back door too much and the middle bit. The rest seems perfectly sound. There's a bit of surface rust on the that middle bit further along where it meets the outer sill but I can sand that back and treat it when I remove the outer sill.
Also do you think it's safe for the middle metal to detach from the inner sill when I am drilling out the spot welds to take off the outer sill? That won't weaken the frame and require bracing too would it? Just trying to cover all the bases.
Thanks
Well it's not the whole inner sill. It's just a 10-20cm bit at the back of the sill at the bottom flange which doesn't go under the back door too much and the middle bit. The rest seems perfectly sound. There's a bit of surface rust on the that middle bit further along where it meets the outer sill but I can sand that back and treat it when I remove the outer sill.
Also do you think it's safe for the middle metal to detach from the inner sill when I am drilling out the spot welds to take off the outer sill? That won't weaken the frame and require bracing too would it? Just trying to cover all the bases.
Thanks
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